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

• Oct 23rd 2012, 03:54 PM
kingsolomonsgrave
after implicitly differentiating an expression, find equation of tangent line at x=a
Attachment 25375

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.
• Oct 23rd 2012, 04:20 PM
Prove It
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.
• Oct 23rd 2012, 04:25 PM
kingsolomonsgrave
Re: after implicitly differentiating an expression, find equation of tangent line at
OH! of course, thanks!