Question

(a+b)²-9a²和9(m+n)²-(m-n)²分解因式,注意分解完

Answer 1

(a+b)²-9a²=a²+2ab+b²-9a²=-8a²+2ab+b²=-(2a-b)(4a+b)

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