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closetgeek
2012-May-30, 04:53 PM
I promise, no one is doing my math homework for me, it's already been done, last week. I got a portion of a problem wrong in my math homework. I can't figure out how it's wrong and I sent a message to my instructor, last week. I haven't heard back from her, yet. I gave my fiance the equation and he came out with the same thing I did, so he can't help me. I was wondering if anyone else can do the equation and see what you come up with.

The question gives the equation 9x -6y = -6 and then asked if either of these two ordered pairs are solutions (4, -8), (10/3, 6).

For (4, -8) I put no, it is not a solution to 9x - 6y = -6 and I got that part correct.

For (10/3, 6) I put yes, it is a solution to 9x -6y = -6 and I got marked wrong by the program.

When I go through the "Help Me Solve" part, it explains every step of the first ordered pair. When I get to the second ordered pair, it stops at

9(10/3) - 6(6) = -6 and just tells you to simplify which is 9(10/3) = 90/3 which = 30 and -6 * 6 = -36.

30 - 36 = -6 so; -6 = -6. However, when I click "yes" it is a solution it tells me this:

"You answered yes. The correct answer is no because when the value of x and y are substituted into the equation, the right and left sides are equal."

I've gone through notes, the textbook and videos and I cannot find a single time when substituting ordered pairs is a true statement but not a solution.

If it's a glich in the system, I want my instructor to change my grade because that one problem is the reason I don't have 100% on my homework. Am I overlooking something or does it look like some sort of computer error?

HenrikOlsen
2012-May-30, 04:58 PM
You're right.

My guess is that someone took a calculator and did 10/3=3.3333333, 3.3333333*9=29.99999, 29.999999-36=6.00000001, 6,0000001 not equal to 6

ShinAce
2012-May-30, 05:04 PM
The second set is a unique solution, so the answer is yes.

Trust me, never worry about 100%. I've had term grades in math of 103% and 104%. I have yet to get an A++. As long as you get an A+, you can't ask for more.

closetgeek
2012-May-30, 05:28 PM
The second set is a unique solution, so the answer is yes.

Trust me, never worry about 100%. I've had term grades in math of 103% and 104%. I have yet to get an A++. As long as you get an A+, you can't ask for more.

I currently have a 93.3% average because I go into anxiety on quizzes and tests. I got an 88% on my only test because for 2 problems, I made stupid errors like 36/9 = 36 (yep, I did that) and on another question, I suddenly forgot how to divide fractions (I forgot to invert). The third mistake, I thought they were asking for a pair of numbers but they were only asking for a specific part of the pair. I need the 100% on lectures, homework, and discussion board to keep my overall average up.

Thank you both for your speedy replies. :)

ShinAce
2012-May-30, 05:33 PM
I need the 100% on lectures, homework, and discussion board to keep my overall average up.

Wait, what? A grade on a discussion board? We only do lectures here, no homework. We don't even do organized lectures, just mostly rambling.

Should have made it a poll so we can grade you!

Cougar
2012-May-30, 05:55 PM
The question gives the equation 9x -6y = -6 and then asked if either of these two ordered pairs are solutions (4, -8), (10/3, 6).

You are correct that (10/3, 6) is a solution to the given equation. Substituting, it boils down to -6=-6, like you got.

I do, however, have a couple of very minor nitpicks. :rolleyes: In the equation 9x - 6y = -6, the minus sign on the left-hand side is the subtraction operator, not the sign of the 6y term. So when you carry out your substitutions:


9(10/3) - 6(6) = -6 and just tells you to simplify which is 9(10/3) = 90/3 which = 30 and -6 * 6 = -36.

...you should get (30) - ((+)36). Of course, (30) + (-36) gives you the same answer, but, well, 6y = 6(6) = 36, not -36.

Also, it is not wrong to figure 9(10/3) = (9*10)/3 = 90/3 = 30. HOWEVER, it just seems easier to divide by the 3 first, so... 9(10/3) = (9/3)(10) = 3(10) = 30. :)

grapes
2012-May-30, 06:45 PM
You're right.

My guess is that someone took a calculator and did 10/3=3.3333333, 3.3333333*9=29.99999, 29.999999-36=6.00000001, 6,0000001 not equal to 6
Except the response was that they were equal. Weird.


"You answered yes. The correct answer is no because when the value of x and y are substituted into the equation, the right and left sides are equal."

The second set is a unique solution, so the answer is yes.
Not unique. There is an infinite number of solutions. The equation represents a straight line, any of the points on the line are solutions.

ShinAce
2012-May-30, 07:01 PM
Not unique. There is an infinite number of solutions. The equation represents a straight line, any of the points on the line are solutions.

Right, but the question asks if the ordered pair is a solution. As given, the second pair is a unique solution to the expression 9x -6y = -6. It most definitely is a unique solution would be my answer to the second part of the question.

Jeff Root
2012-May-30, 07:20 PM
What Cougar pointed out about what the minus sign is
attached to is what caught my attention. Did you submit
your working of the problem? Even though you get the right
answer, applying the minus sign incorrectly invalidates it.

On the other hand, 90/3 was a lot more obvious to me than
9(10/3).

-- Jeff, in Minneapolis

ShinAce
2012-May-30, 07:26 PM
"You answered yes. The correct answer is no because when the value of x and y are substituted into the equation, the right and left sides are equal."


Do you mind trying it again, because that sentence doesn't make sense. Does it say that the right and left sides are equal or are not equal. Either way, it's still just a typo on the teachers part.

Jeff Root
2012-May-30, 07:32 PM
The meaning of that sentence is ambiguous.

-- Jeff, in Minneapolis

ShinAce
2012-May-30, 07:40 PM
If only I could figure out what ambiguous means.

Closetgeek: I like you dog! It's cute.

Jeff Root
2012-May-30, 07:56 PM
The meaning of my statement was ambiguous, too, I see.

I meant that "The correct answer is no because when the
value of x and y are substituted into the equation, the right
and left sides are equal" could refer to what happens when
correct values of x and y are used, or it could refer to what
happens when the suggested values are used.

-- Jeff, in Minneapolis

closetgeek
2012-May-30, 07:59 PM
What Cougar pointed out about what the minus sign is
attached to is what caught my attention. Did you submit
your working of the problem? Even though you get the right
answer, applying the minus sign incorrectly invalidates it.

On the other hand, 90/3 was a lot more obvious to me than
9(10/3).

-- Jeff, in Minneapolis

No I don't have to type anything out. The instructor on the videos always assigns the minus sign as a negative to the following number. It's just become habit for me to read it that way, now.

closetgeek
2012-May-30, 08:00 PM
Do you mind trying it again, because that sentence doesn't make sense. Does it say that the right and left sides are equal or are not equal. Either way, it's still just a typo on the teachers part.

It reads exactly as I wrote it. I thought maybe my blind spot was messing with me again, so I asked the Mr. to read it allowed as I typed it. It won't let me copy and paste from the page, though. It's not the teacher, this work is from an online text book, program.

closetgeek
2012-May-30, 08:11 PM
Here is a screen shot of first, the homework page, and then the help me solve it page.

16966

16967

ShinAce
2012-May-30, 08:23 PM
The meaning of my statement was ambiguous, too, I see.
-- Jeff, in Minneapolis

I was just being sarcastic.

It appears there's been a glitch in the matrix causing your homework grade to be captured by agents. Any rescue attempt is going to be risky without the oracle's advice.

Jeff Root
2012-May-30, 08:54 PM
It prompted me to specify the ambiguity I had in mind.
Without that, my assertion was lame.

-- Jeff, in Minneapolis

Solfe
2012-May-30, 09:57 PM
I promise, no one is doing my math homework for me, it's already been done, last week. I got a portion of a problem wrong in my math homework. I can't figure out how it's wrong and I sent a message to my instructor, last week. I haven't heard back from her, yet. I gave my fiance the equation and he came out with the same thing I did, so he can't help me. I was wondering if anyone else can do the equation and see what you come up with.

The question gives the equation 9x -6y = -6 and then asked if either of these two ordered pairs are solutions (4, -8), (10/3, 6).

For (4, -8) I put no, it is not a solution to 9x - 6y = -6 and I got that part correct.

For (10/3, 6) I put yes, it is a solution to 9x -6y = -6 and I got marked wrong by the program.

When I go through the "Help Me Solve" part, it explains every step of the first ordered pair. When I get to the second ordered pair, it stops at

9(10/3) - 6(6) = -6 and just tells you to simplify which is 9(10/3) = 90/3 which = 30 and -6 * 6 = -36.

30 - 36 = -6 so; -6 = -6. However, when I click "yes" it is a solution it tells me this:

"You answered yes. The correct answer is no because when the value of x and y are substituted into the equation, the right and left sides are equal."

I've gone through notes, the textbook and videos and I cannot find a single time when substituting ordered pairs is a true statement but not a solution.

If it's a glich in the system, I want my instructor to change my grade because that one problem is the reason I don't have 100% on my homework. Am I overlooking something or does it look like some sort of computer error?

That looks exactly like mathxl.com.

EDIT - I am an idiot. I didn't see the screen shots. There are some little glitches in mathxl, but nothing too terrible. Then again, the glitches would stop you from getting a 100% on the homework.

closetgeek
2012-May-30, 10:12 PM
I was just being sarcastic.

It appears there's been a glitch in the matrix causing your homework grade to be captured by agents. Any rescue attempt is going to be risky without the oracle's advice.

I already sought out the oracle. She only speaks in binary so I am screwed!

Moose
2012-May-31, 12:31 AM
Just to butt in: Your answer is correct. The second ordered pair is a valid solution. The error message is incorrectly applied and internally contradictory.

Solfe
2012-May-31, 03:17 AM
Is this this class College Mathematics (Mine was MT-125)? I had a similar issue with mathxl.com in this thread (http://www.bautforum.com/showthread.php/130475-Stupid-Homework-Question-The-English-of-Math?). My question involved pairs numbers for mid-points and it did some really weird stuff to me.

jokergirl
2012-May-31, 03:32 AM
If I was you, I would tell the teacher to ask for their money back for that computer program...

;)

Tobin Dax
2012-Jun-01, 03:38 PM
If I was you, I would tell the teacher to ask for their money back for that computer program...

;)

It's fairly widely used, as I understand it. Luckily, I don't teach math.

cg, all I really know about MathXL is that it can do weird things sometimes. What did your teacher say when you asked about it?

closetgeek
2012-Jun-02, 10:10 PM
It's fairly widely used, as I understand it. Luckily, I don't teach math.

cg, all I really know about MathXL is that it can do weird things sometimes. What did your teacher say when you asked about it?

She said she spoke to someone at the program about the problem and being it was holiday weekend, that it should be fixed by Wed. As of last Wed, it hadn't been fixed. On Thursday, I emailed my teacher again but I haven't heard back yet. Friday I got on chat with support at MathXL and they told me that my teacher needs to go in and fix the grade. I told her that there is still the problem with the question and she told me to contact my teacher.

Tobin Dax
2012-Jun-02, 11:41 PM
She said she spoke to someone at the program about the problem and being it was holiday weekend, that it should be fixed by Wed. As of last Wed, it hadn't been fixed. On Thursday, I emailed my teacher again but I haven't heard back yet. Friday I got on chat with support at MathXL and they told me that my teacher needs to go in and fix the grade. I told her that there is still the problem with the question and she told me to contact my teacher.

Sorry you're not getting anywhere. I can understand that your teacher needs to fix your grade, and I'd probably just worry about that right now. Fixing the question will likely take some time to happen.

Hornblower
2012-Jun-03, 11:43 AM
Our teachers and administrators need to have their acts together and have a plan B ready in case a buggy computer program evaluates a student's best efforts incorrectly.

Tobin Dax
2012-Jun-03, 09:28 PM
Most teachers do, IME. Heck, if I'm ready for it . . . . :)

DoggerDan
2012-Jun-04, 08:29 AM
For (10/3, 6) I put yes, it is a solution to 9x -6y = -6 and I got marked wrong by the program.

You're correct. Program's wrong.

closetgeek
2012-Jun-06, 04:10 PM
Here's the rub. Apparently there were two gliches in that assignment. I checked the score and it was the same, after my teacher said it had been corrected. Now, I got the last problem wrong. I looked at the answer and can't figure out how I arrived at that conclusion, but it's unlikely that someone got spiteful and went in to change my answer. The glich has been corrected by my score remains the same. :(

On another note; is it my nerd showing or are solving word problems, linear equations in 2 and 3 variables kind of fun?

On another note; our weekly assignment is broken up into teams of three. We are given a word problem and we have to create formulas to find the answers. The teams are supposed to work through the problem on the discussion board. I put up a post to start the thread on Monday and got no response. I sent private messages to my team and still got no response. WTH? Really? I am the type to get the discussion board questions done ASAP. There are about 5 of us that get the DB problems done on the day it's assigned. She couldn't stick me with that group? She had to put me in the group that pathologically leave everything for the last minute?

ShinAce
2012-Jun-06, 04:26 PM
Sorry, but LOL!!! Instead of just fixing the known problem, it seems the teacher redid the entire assignment. Hopefully, you can leave it behind you and laugh it off. Just remember that the final exam won't be MathXL based.

Welcome to higher learning. I think I am the only guy that likes to get assignments done early. Of course, when I was in electrical engineering at the age of 18 I would leave everything to the last second and do a minimal type job. Now I'm a few years older and have seen a few things in the world. I do the best job I can with my schoolwork since the only person that can affect that grade is ME. Find chicks to group up with, they're usually much better at time management than 19 year old boys.

Tobin Dax
2012-Jun-06, 06:17 PM
On another note; is it my nerd showing or are solving word problems, linear equations in 2 and 3 variables kind of fun?
Take physics next. It's all word problems. :)


On another note; our weekly assignment is broken up into teams of three. We are given a word problem and we have to create formulas to find the answers. The teams are supposed to work through the problem on the discussion board. I put up a post to start the thread on Monday and got no response. I sent private messages to my team and still got no response. WTH? Really? I am the type to get the discussion board questions done ASAP. There are about 5 of us that get the DB problems done on the day it's assigned. She couldn't stick me with that group? She had to put me in the group that pathologically leave everything for the last minute?
Have you tried setting up a time (day, hour, something) to work on these problems with your group? Try to find a regular time that fits everyone's schedule and get them to commit to it. Otherwise you're just going to end up waiting until they want to respond, as you are now. This is how it goes in asynchronous learning.

closetgeek
2012-Jun-06, 06:56 PM
Take physics next. It's all word problems. :)


Have you tried setting up a time (day, hour, something) to work on these problems with your group? Try to find a regular time that fits everyone's schedule and get them to commit to it. Otherwise you're just going to end up waiting until they want to respond, as you are now. This is how it goes in asynchronous learning.

I think I need physics for my Bachelor so it's not an option. I've always wanted to understand physics, anyway so I do look forward to it. My biology lab partner is currently taking Calc 3 and he was explaining it to me. He said if I am enjoying what I am doing now, I will like Calc 1 and 3, but 2 is awful. The only thing that makes me nervous is, some of our assignments require plugging in test numbers. I am going to join the live office hours and speak with my instructor about that. Hopefully she will have some advice.

My first post in the group thread was basically saying when I am available because it might be better if we are all on at the same time. I am open to suggestions, though. We have two and a half days left to complete the assignment and still nothing.

HenrikOlsen
2012-Jun-06, 08:02 PM
What group assignments are supposed to teach you:
10% Communication
10% Responsibility
10% Collaboration
70% Teamwork
What group assignments really teach you:
5% Communication
5% Responsibility
5% Collaboration
5% Teamwork
80% Trust no one.

ShinAce
2012-Jun-06, 08:39 PM
I will like Calc 1 and 3, but 2 is awful.

I would say the same, but you shouldn't need calc 2 or 3. I did calc 2 when I was enrolled in electrical engineering, then did calc 3 after switching to physics. Stats was fun as far as math goes, but calc 1 and 3 are definitely the most rewarding in terms of understanding. Calc 2(differential equations and numerical methods) is just a grind, so to speak.

Tobin Dax
2012-Jun-06, 11:32 PM
I just need to quit trying to give you advise, cg. You seem to be on top of everything (as much as you can be, anyway).

I'm not sure what your Calc 1, 2, and 3 are, and I'm a bit too far removed to comment on it. However, ShinAce seems to have a completely different definition of those courses than I do.

ShinAce
2012-Jun-07, 09:30 PM
For me, calculus was broken up as:
-high school, or pre-calc, being the limit and a bunch of derivatives plus the basic concept of the integral

From the Carleton university site
-calc 1: Definite and indefinite integrals; numerical approximation. Transcendental functions (trigonometric and inverse trigonometric, logarithm and exponential), their derivatives and integrals. Applications: area, volume, average value. Further techniques of integration: integration by parts, partial fractions, and substitutions.
-calc 2: First-order differential equations. Linear differential equations with constant coefficients; undetermined coefficients; annihilator operators. Variation of parameters. Euler-Cauchy differential equation. Indeterminate forms. Sequences and series; convergence tests; estimation of sums. Power series, Taylor series, remainders. Use of power series to solve differential equations.
Restricted to students in the Faculty of Engineering, or in B.Sc. programs of the Department of Physics
Note* This is usually still a first year course
-calc 3: Fourier series; expansions for even and odd functions; half-range expansions. Surfaces in R3. Differential calculus of functions of several variables. Extrema and Lagrange multipliers. Exact differentials. Line integrals. Double integrals; polar coordinates; applications. Triple integrals; cylindrical and spherical coordinates; applications.

I think I have one left(without checking my degree requirements), a third year calc. Let's call it calc 4:
"Laplace transforms, Fourier series and Fourier transforms, solutions of partial differential equations of mathematical physics, boundary value problems, applications."

I enjoyed Fourier series because I'm an audio buff, and that material is the basis of waveforms. I also found multivariable calculus to be the most powerful tool ever presented to me. Finally, geometry started to make sense. In high school, a circle was a circle, an ellipse an ellipse, a parabola a parabola, and so forth. After multivariable calculus, you see them as simply conic sections. That's when you really begin to visualize a problem and a solution as shapes.

As far as I can tell, closetgeek is doing linear algebra. Without knowing what program this is for, it's hard to give specific advice about math in the future.

closetgeek
2012-Jun-08, 03:03 AM
HenrikOlsen, I want to laugh but I am beginning to think that is 100% accurate.

Tobin Dax, don't even worry about it. The Calc was merely for conversation. I have a good way to go before I get there. I spoke with my instructor, again, though she's probably getting sick of me; she said as long as it shows that I am making the effort for teamwork, I will get the points, they won't. One teamate finally responded to say when she is available but hasn't posted since. The other, I looked through the DB and he hasn't posted any assignments since the first week so I think he is dropping the class. I finally took control, this morning and posted responsibilities to the other team member and said, "if you don't like the tasks I assigned, you had four days to take the reins. Please don't wait till the last minute to do this because the funny thing about unforseeable events is that you don't see them coming."

ShinAce, you've just convinced me, with all those scary sounding titles, that mathematicians are dedicated to keeping the Pythagorian tradition of scaring off the laypeople; annihilator operators? Transcendental functions? Is this still math or the apocalypse.

Solfe
2012-Jun-08, 05:09 AM
What group assignments are supposed to teach you:
10% Communication
10% Responsibility
10% Collaboration
70% Teamwork
What group assignments really teach you:
5% Communication
5% Responsibility
5% Collaboration
5% Teamwork
80% Trust no one.

So very true. The fuzzy English/Social Science "What do you think it means?" group projects are a nightmare, I can't even imagine one in a math class.

Tobin Dax
2012-Jun-08, 01:15 PM
Tobin Dax, don't even worry about it. The Calc was merely for conversation. I have a good way to go before I get there. I spoke with my instructor, again, though she's probably getting sick of me; she said as long as it shows that I am making the effort for teamwork, I will get the points, they won't. One teamate finally responded to say when she is available but hasn't posted since. The other, I looked through the DB and he hasn't posted any assignments since the first week so I think he is dropping the class. I finally took control, this morning and posted responsibilities to the other team member and said, "if you don't like the tasks I assigned, you had four days to take the reins. Please don't wait till the last minute to do this because the funny thing about unforseeable events is that you don't see them coming."
Now I'm curious about your group work. Is it all supposed to be done on the discussion boards? Are these with the "regular" discussion boards (assuming there are some) or are they separate? I've considered assigning group work in online courses, but I've never been quite sure how well it would work.


ShinAce, you've just convinced me, with all those scary sounding titles, that mathematicians are dedicated to keeping the Pythagorian tradition of scaring off the laypeople; annihilator operators? Transcendental functions? Is this still math or the apocalypse.
That's the big, scary stuff. Your lab partner is probably working on things in ShinAce's Calc 1 class, since his class appears to be a year long.

ShinAce
2012-Jun-08, 03:14 PM
Let's face it, you don't guess your way through it. I laughed a bit when we redid basic geometry in calc 3. "ok class, this is a point. That's a line. Do these two lines intersect? Where?" Which is what you posted as a question. It's two planes that intersect to form a line, in 3d. I thought to myself, am I back in high school. Our final exam boiled down to translating the word salad of a problem into an integral.

Turn problem into a function. Use conditions to set limits on the function. Solve.

ShinAce
2012-Jun-08, 03:27 PM
Also, we never learnt the annihilator operator. We solved the homogeneous equation first, which I can do in mere seconds. Then we used the 'Wronskian' to find a particular solution. I took calc 2 over 10 years ago and again this year as a refresher and both times we did not use the annihilator operator. Don't be scared, solving a 2nd order homogeneous diff equation is a question of factorizing a degree 2 polynomial. We did a lot of that in higj school. The old, find the roots of x^2 + x - 6 = 0. Done. Yeah, the quadratic formula gets used on occasion in calc.

closetgeek
2012-Jun-08, 05:59 PM
Now I'm curious about your group work. Is it all supposed to be done on the discussion boards? Are these with the "regular" discussion boards (assuming there are some) or are they separate? I've considered assigning group work in online courses, but I've never been quite sure how well it would work.


I don't get it either. She gave us the information we need and we are supposed to work together on the discussion board to come up with a system of two equations in two unknowns for the first part of the assignment. Coming up with the equations is easy, working together with other people on the discussion board doesn't seem possible without one person doing all the work and the others saying, "yeah yeah, that's right." If you did the math homework due, prior to this assignment, you either look at the information and know how to write the equation or you don't. I don't know how to work with other people to create an equation I already know how to write out. Then the second part is to solve it in algabraic terms, in a table, and one guess and check solution. I think that is where the team leader is supposed to delegate tasks to everyone. One person solves the algebraic, one person does the table, and then one person does the guess check solution. My biggest problem with the third is, I don't know how to guess check without already knowing a system to guess and check correctly. I either have to guess/check, knowing up front that my answer is correct, or intentionally guess check with wrong numbers, just to show how inaccurate guess check can be when looking for exact numbers.