Verified answer

[tex]\displaystyle (x-2)^2+8x=(x-1)(x+1)\\x^2-4x+4+8x=x^2-1\\-4x+4+8x=-1\\4x+4=-1\\4x=-1-4\\4x=-5\\\\x=-\frac{5}{4}=-1\frac{1}{4}=-1,25[/tex]