(x^2-√2x+1)(x^2+√2x+1)-(x^2-x+1)(x^2+x+1)
=[(x^2+1)^2-(√2x)^2]-[(x^2+1)^2-x^2]
=(x^2+1)^2-(√2x)^2-(x^2+1)^2+x^2
=x^2-(√2x)^2
=x^2-2x^2
=-x^2