(x-2y)？ *(x+2y)？ *(x？ +4y？ )?

=[(x-2y)(x+2y)]？ *(x？ +4y？ )?

=(x？ -4y？ )? *(x？ +4y？ )?

=(x？ - 16y？ )?

=x^8-32x？ y？ +256y^8

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