Question

把下列各式分解因式⒈-m^3n^2+4m^2n-mn ⒉25(m-n)^2-4(m+n)^2⒊-9x^3+18x^2-9

Answer 1

2.原式=[5（m-n）+2(m+n)][5(m-n)-2(m+n)]

=(7m-3n)(3m-7n)

3.原式=-9(x^2-2x+1)

=-9(x-1)^2

4.原式=(x+y)^2+4(x+y)+4

=(x+y+2)^2