# Math Help - after implicitly differentiating an expression, find equation of tangent line at x=a

1. ## after implicitly differentiating an expression, find equation of tangent line at x=a

I differentiated $x^2+y=xy$ to get the above equation.

Then I am asked to find the equation of the tangent line when x=3, I must find the y value for the expression how does one do that? When I plug in x=3 I can solve for $y= 6-2y'$

but I don't know where to go from there.

2. ## Re: after implicitly differentiating an expression, find equation of tangent line at

Plug x = 3 into your original equation \displaystyle \begin{align*} x^2 + y = x\,y \end{align*} to get the corresponding y value.

3. ## Re: after implicitly differentiating an expression, find equation of tangent line at

OH! of course, thanks!