Math Help - Implicit differentitaion

1. Implicit differentitaion

Find dy/dx :
(9/x)+(9/y)=4

My answer is ((xy)^2 - 9y^2)/-9x^2

My answer is not matching with the correct answer. Is it wrong ?
Can u help me.

2. Originally Posted by kashifzaidi
Find dy/dx :
(9/x)+(9/y)=4

My answer is ((xy)^2 - 9y^2)/-9x^2

My answer is not matching with the correct answer. Is it wrong ?
Can u help me.

$\frac{9}{x}+\frac{9}{y}=4$

$-\frac{9}{x^2}-\frac{9}{y^2}y'=0$

$y'=-\frac{y^2}{x^2}$