Let xy=1

and let dy/dt=5

Find dx/dt when x=5

Question

Let xy=1

and let dy/dt=5

Find dx/dt when x=5

raspberryjam · Answer

Okay so the first step is to take the derivative of xy=1. Don't forget the product chain rule!
$$ xy=1$$
$$ x\frac{dy}{dt}+y\frac{dx}{dt}=0$$
Then just plug everything in!
$$ (5)(5)+5\frac{dx}{dt}=0$$
and solve for $$\frac{dx}{dt}$$

anonymous · Answer

then the answer would be -5. If i multiply the two five's together , i get 25. move it to the other side and divide by 5 i get -5. When i submit that answer on my end, it comes out wrong.

anonymous · Answer

The method was correct.

raspberryjam · Answer

Hmm...it should be right. Double check the numbers in the question?

anonymous · Answer

YEAH its still saying its wrong.

raspberryjam · Answer

Ahh wait my mistake.
I accidentally put in 5 for y. So solve for y first. and put that in instead of the 5*dx/dt.

anonymous · Answer

$$y=\frac{1}{5}|x=5$$We're given the value for $y$. As I said, the method is correct.