(x^2+2)^2-(2x-1)^2
=[(x^2+2)+(2x-1)][(x^2+2)-(2x-1)]
=[x^2+2+2x-1][x^2+2-2x+1]
=(x^2+2x+1)(x^2-2x+3)
=(x+1)^2(x^2-2x+3)