(m加n)2次方减4(m2次方减n2次方)加4(m减n)2次方

问题描述:

(m加n)2次方减4(m2次方减n2次方)加4(m减n)2次方

答:
(m+n)²-4(m²-n²)+4(m-n)²
=m²+2mn+n²-4m²+4n²+4(m²-2mn+n²)
=m²-6mn+9n²
=(m-3n)²