First, move all the terms to one side
x^2+4x-4-8=0
Then, simplify.
x^2+4x-12=0
After that, factor. Ask yourself: Which two numbers add up to 4 and multiply to -12? That would be -2 and 6. Then, rewrite the expression.
(x-2)(x+6)=0
Lastly, solve for x.
x=2, -6
Your final answer would be x = -6 or x = 2