p²-p²q+pq²r = a²-ax+ay-xy= p²+pq-qr-pr=

p²-p²q+pq²r = p(p-pq+q²r)

a²-ax+ay-xy = a(a-x)+y(a-x) = (a+y)(a-x)

p²+pq-qr-pr = p(p+q)-r(q+p) = (p-r)(p+q)