(m-2n+3)(m+2n-3)计算,

问题描述:

(m-2n+3)(m+2n-3)计算,

(m-2n+3)(m+2n-3)
=[(m-2n)+3][(m+2n)-3]
=(m-2n)^2-3^2
=m^2-4mn+4n^2-9