x(p-q)-y(p-q)+z(q-p)
=x(p-q)-y(p-q)-z(p-q)
=(p-q)(x-y-z)
25(x+y)^2-16(x-y)^2
=[5(x+y)+4(x-y)][5(x+y)-4(x-y)]
=(5x+5y+4x-4y)(5x+5y-4x+4y)
=(9x+y)(x+9y)
p^2(p+q)^2-q^2(p-q)^2
=[p(p+q)+q(p-q)][p(p+q)-q(p-q)]
=(p^2+pq+pq-q^2)(p^2+pq-pq+q^2)
=(p^2+2pq-q^2)(p^2+q^2)
4-(3a+2b)^2
=(2+3a+2b)(2-3a-2b)
(x^2+4)^2-16x^2
=(x^2+4+4x)(x^2+4-4x)
=(x+2)^2(x-2)^2