Quote (m0hawk @ Feb 27 2014 07:14pm)
Here's how id do it:
-the equation of the tangent for x=a is y=f'(a)(x-a)+f(a)
-the tangent passes through (0,0) iff x=0 and y=0, thus it passes through (0,0) iff 0=-af'(a)+f(a)
-thus, the answers are the solutions to the equation -a^2+4=0 , so (2,8) and (-2,8) are the solutions.
I'm lost even at this lol,