解1: x³+x²y-xy²-y³
=x^3-y^3+x^2y-xy^2
=(x+y)(x^2-xy+y^2)+xy(x+y)
=(x+y)(x^2+y^2)
解2.a²-b²+a+b
=（a+b）(a-b)+a+b
=(a+b)(a-b+1)
解3.16-1/25m²
=（4+m/5）(4-m/5)