Question

分解因式9(m-n)²-25(m+n)²

Answer 1

原式=3²(m-n)²-5²(m+n)²

=[3(m-n)]²-[5(m+n)]²

=[3(m-n)-5(m+n)]*[3(m-n)+5(m+n)]

=(3m-3n-5m-5n)(3m-3n+5m+5n)

=(-2m-8n)(8m+2n)

=-4(m+4n)(4m+n)