Originally Posted by

**RezMan** Hey guys can you help me out with this:

** Given the ellipse 4x^2 + 9y^2 = 36,**

**a) Find **$\displaystyle \frac{dy}{dx}$.

is this correct:

$\displaystyle \frac{d(4x^2}{dy}+\frac{9y^2}{dx}*\frac{dy}{dx} = \frac{d(36)}{dx}$

$\displaystyle 8x+18y*\frac{dy}{dx}=0 $

$\displaystyle \frac{dy}{dx}=-\frac{4x}{9y} $

**b) Give the equations of all tangent lines to the graph at ***x* = 1.

at this point I plug in x in the original function to get y right?

I got this weird number for y when I did that: $\displaystyle y=\pm \frac{4\sqrt{2}}{3} $

are my calculations correct?