1.4(x-y)²-z² 2.-16x的四次方+y的四次方

1.4(x-y)²-z²
=[2(x-y)]²-z²
=(2x-2y+z)(2x-2y-z)
2.-16x的四次方+y的四次方
=y的4次方-16x的4次方
=(y²+4x²)(y²-4x²)
=(y²+4x²)(y+2x)(y-2x)
3.4x²-25（x-y）²
=[2x+5(x-y)][2x-5(x-y)]
=(7x-5y)(5y-3x)
4.（x-2y）²-20（x-2y）
=(x-2y)(x-2y-20)
5.4x的四次方-64
=4(x的4次方-16)
=4(x²+4)(x²-4)
=4(x²+4)(x+2)(x-2)