1. Derivative Help

find y' if y=x/(x+y)

Do you take the derivative of the y on the left of the = or no?

I really need help

2. Originally Posted by rawkstar
find y' if y=x/(x+y)

Do you take the derivative of the y on the left of the = or no?

I really need help
to make it a bit easier, multiply both sides by (x+y) to clear the fraction ...

$y(x+y) = x$

$xy + y^2 = x$

now take the derivative implicitly ...

$xy' + y + 2y \cdot y' = 1$

$xy' + 2y \cdot y' = 1 - y$

$y'(x + 2y) = 1 - y$

$y' = \frac{1-y}{x+2y}$