6q(p-q)-4p(p+q)
=6pq-6q²-4p²-4pq
=-4p²+2pq-6q²
=-2(2p²-pq+3q²)
.
x(x-y)²-y(y-x)²
=x(x-y)²-y(x-y)²
=(x-y)(x-y)²
=(x-y)³
.
x(x+y)(x-y)-x(x+y)²
=x(x+y)[(x-y)-(x+y)]
=-2xy(x+y)