Question

(x-2y) (x²+4y²)(x+2y)-x4

Answer 1

(x-2y)(xˇ2+4yˇ2)(x+2y)-xˇ4=(x-2y)x+2y)(xˇ2+4yˇ2)-xˇ4=
=(xˇ2-4yˇ2)(xˇ2+4yˇ2)-xˇ4=
=xˇ4-16yˇ4-xˇ4=-16yˇ4