(3m-2n)^+(3m+2n) (3m-2n)-9(m+n)^
问题描述：
(3m-2n)^+(3m+2n) (3m-2n)-9(m+n)^
答
(3m-2n)²+(3m+2n) (3m-2n)-9(m+n)²
=(3m-2n)²-9(m+n)²+(3m+2n) (3m-2n)
=(3m-2n+3m+3n)(3m-2n-3m-3n)+9m²-4n²
=-5n(6m+n)+9m²-4n²
=-30mn-5n²+9m²-4n²
=9m²-9n²-30mn