Verified answer

4(x+2)^2 - 2(x^2-4) - (x-2)^2=x^2;

4(x^2+4x+4) - 2x^2 +8 - (x^2-4x+4)=x^2;

4x^2+16x+16  - 2x^2 +8 - x^2+4x-4 - x^2=0;

20x+20=0;

20x=-20;

x=-1.