1) ..........=(a+b)(a²-ab+b²) -2ab(a+b)=(a+b)( -ab-2ab)= -3ab(a+b)
2) ..........=(m-n)(m²+mn+n²)-6m(m²+mn+n²)=(m²+mn+n²)(m-n-6m)=(m²+mn+n²)(-5m-n)
3) ........=(x-y)(x²+xy+y²)+8xy(x-y)=(x-y)(x²+xy+y²+8xy)=(x-y)(x²+9xy+y²)
4) ......=(p+q)(p²-pq+q²) -2pq(p²-pq+q²)=(p²-pq+q²)(p+q-2pq)