# Need help with a few important homework questions

• April 28th 2008, 07:57 PM
sean1058
Need help with a few important homework questions
Graph y^2=2xy

The thing with this is that I just don't know how to solve for Y. Apparently I'm not supposed to divide Y from both sides?

Also I have no idea how to do this next one.

A machine is rolling a metal cylinder under pressure. The radius of the cylinder is decreasing at a constant rate of 0.05 inches per second and the volume is a constant 128(pi) cubic inches. At what rate is the length h changing when the radius r is 1.8 inches?

And I'll just throw in this third one cuz I'm not sure if I did it right.

What Values of c are guaranteed by the Mean Value Theorem for f(x)=(x-2)^3 on the interval [-1,2]?

I got 2-(the square root of)3.

Thanks
• April 28th 2008, 08:01 PM
Mathstud28
Quote:

Originally Posted by sean1058
Graph y^2=2xy

The thing with this is that I just don't know how to solve for Y. Apparently I'm not supposed to divide Y from both sides?

Also I have no idea how to do this next one.

A machine is rolling a metal cylinder under pressure. The radius of the cylinder is decreasing at a constant rate of 0.05 inches per second and the volume is a constant 128(pi) cubic inches. At what rate is the length h changing when the radius r is 1.8 inches?

And I'll just throw in this third one cuz I'm not sure if I did it right.

What Values of c are guaranteed by the Mean Value Theorem for f(x)=(x-2)^3 on the interval [-1,2]?

I got 2-(the square root of)3.

Thanks

For the first one just plot points..if you have to

for the mean value one did you solve for c in the following

$3(c-2)^2=\frac{0+9}{2+1}$?
• April 28th 2008, 08:07 PM
sean1058
No I have this

$3(c-2)^2=\frac{0+27}{2+1}$

cuz the 3 is to the third power

and I can't just plot points for that one, I have to solve it first.
• April 28th 2008, 08:21 PM
Mathstud28
Quote:

Originally Posted by sean1058
Graph y^2=2xy

The thing with this is that I just don't know how to solve for Y. Apparently I'm not supposed to divide Y from both sides?

Also I have no idea how to do this next one.

A machine is rolling a metal cylinder under pressure. The radius of the cylinder is decreasing at a constant rate of 0.05 inches per second and the volume is a constant 128(pi) cubic inches. At what rate is the length h changing when the radius r is 1.8 inches?

And I'll just throw in this third one cuz I'm not sure if I did it right.

What Values of c are guaranteed by the Mean Value Theorem for f(x)=(x-2)^3 on the interval [-1,2]?

I got 2-(the square root of)3.

Thanks

$y^2-2xy=0\Rightarrow{(y-x)^2-x^2=0}$
so $(y-x)^2=x^2\Rightarrow{|y-x|=|x|}\Rightarrow{y=x\pm|x|}$
• April 28th 2008, 09:28 PM
elizsimca
Quote:

Originally Posted by sean1058
Graph y^2=2xy

The thing with this is that I just don't know how to solve for Y. Apparently I'm not supposed to divide Y from both sides?

Thanks

Well, you can't divide each side by y because it's $y^2$, so to undo that you would have to take the square root to get plain old y.

Do you know polar coordinates? That could help possibly. Otherwise, the comment above this one is the best you will get.
• April 29th 2008, 05:29 AM
sean1058
thanks

if anybody can help me with that middle one it would be most appreciated
• April 29th 2008, 06:05 AM
sean1058
nevermind i got it