Ok here is what I did. I'm kinda weak from factoring

$\displaystyle f(x)= 2x^2+8x-2$

group:

$\displaystyle f(x)= (2x^2+8x)-2$

Completing the Square:

$\displaystyle f(x)= (2x^2+8x+16-16)-2$

$\displaystyle f(x)= (2x^2+8x+16)-16-2$

$\displaystyle f(x)= (2x^2+8x+16)-18$

Factoring:

$\displaystyle f(x)= 2(x^2+4x+8)-18$

Where did I go wrong from here?

$\displaystyle f(x)= 2(x+2)-18$

bcoz if I FOIL 2(x+2)(x+2) it will come out:

$\displaystyle 2(x^2+4x+4)$