a3-5a2b+6ab2
=a(a²-5ab+6b²)
=a(a-2b)(a-3b)
7(x+y)3-5(x+y)2-2(x+y)
=(x+y){7(x+y)²-5(x+y)-2}
=(x+y){7(x+y)+2}{(x+y)-1}
=(x+y)(7x+7y+2)(x+y-1)