Question 104710
Here's the step where you got on the wrong path. 
{{{x-3=(9+x^2)/4}}} 
You're missing a term. 
{{{(A+B)^2=A^2+highlight(2AB)+B^2}}}
Re-work {{{(3-x)^2}}}and continue from there.
You're on the right track otherwise. 
Post another question if you get stuck.