(m+2)^2-9(m-1)^2 平方差
=[(m+2)-3(m-1)][(m+2)+3(m-1)]
=(m+2-3m+3)(m+2+3m-3)
=(5-2m)(4m-1)
(x-y)(x^2+xy+y^2)-xy(y-x)提取公因式
=(x-y)(x^2+xy+y^2)+xy(x-y)
=(x-y)[(x^2+xy+y^2)+xy]
=(x-y)(x^2+xy+y^2+xy)
=(x-y)(x^2+2xy+y^2)完全平方公式
=(x-y)(x+y)^2
3(x-1)^2-18(x-1)+27 提取公因式
=3[(x-1)^2-6(x-1)+9]完全平方公式
=3(x-1-3)^2
=3(x-4)^2
9*1.2^2-16*1.4^2平方差
=(3*1.2-4*1.4)(3*1.2+4*1.4)
=(3.6-5.6)(3.6+5.6)
=-2*9.2
=-18.4