3x平方-9x
=3x(x-3)
-8a平方b平方-4a平方b+2ab
=-2ab(4ab+2a-1)
m的立方(a-2)+m(2-a)
=m的立方(a-2)-m(a-2)
=m(a-2)[m²-1]
=m(a-2)(m+1)(m-1)