-m四次方+m²n²

问题描述:

-m四次方+m²n²
(1)-m四次方+m²n²
(2)4(m+n)²-9(m-n)²
(3)(5a-b)²+20ab

-m四次方+m²n²
=m²n²-m四次方
=m²(n²-m²)
=m²(n-m)(n+m)