Calculus help anyone?

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Dustin_m

Dustin_m

Member
I have an exam tomorrow and I'm trying to get the last of the hw done for it. I'm working on related rates, and I'm f'ing stuck. I can't stand that this fucking book will go through the section showing examples that are really clear, but then the first damn review question will throw something at you that is completely different than anything in the chapter.

The problem I'm stuck on is this:
Equation: 4x^2 + 9y^2 = 1
Given that dx/dt = 3, find dy/dt when
(x,y) = (1/(2sqrt2),1/(3sqrt2)
Click to expand...

I'm not really looking for the answer, but more of how to approach it.
 
you have to use implicit differentiation to find the derivative of the equation.

this will give you an equation in terms of x, y, dx/dt, and dy/dt.

x, y, and dx/dt are all given, so you just use substitution and algebra to solve for the only unknown, dy/dt.

i did a quick 5min search on google and found a bunch of videos on related rates since i initially didnt know how to approach the problem and a quick refresh on this part of calculus. my method seemed right as i got an integer for an answer. does your book have an answer key to see if i'm right?
 
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GSRCRXsi said:
you have to use implicit differentiation to find the derivative of the equation.

this will give you an equation in terms of x, y, dx/dt, and dy/dt.

x, y, and dx/dt are all given, so you just use substitution and algebra to solve for the only unknown, dy/dt.

i did a quick 5min search on google and found a bunch of videos on related rates since i initially didnt know how to approach the problem and a quick refresh on this part of calculus. my method seemed right as i got an integer for an answer. does your book have an answer key to see if i'm right?
Click to expand...

Says the answer should be -2. I'll check out youtube for some vids. I forgot that for the last exam I found a bunch of good vids on there. Thanks
 
thats what i got. -2. do exactly what i said. this problem is VERY straighforward. if you want me to break down what i did step by step so you can see it, id be happy to.
 
I got it. I guess I didn't get that I had to "d/dt" both sides of the equation to start off. thanks

Gotta start going to class religiously, lol. Up until this point I could easily just do the homework and do well on tests, but this calc book is pretty scarce on explanations for stuff. F me, this is only calc 1 and I have at least 3 more semesters of math after this.
 
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im with you. i hated math, although i did well up through calc2. calc 3 and 4 got a bit ridiculous and i stoped caring.
 
Yea, I'm not looking forward to it. Next semester will start to get hard with Calc 2 and Physics 1, machine/assembler, and data structures, plus probably one more class thrown in there so I can finish up sooner.
 
Physics 1 was a lot of fun. Assembly was just time conuming. Data structures wasn't too bad. I hated Calc2, my teacher sucked.
 
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