Question

add p(p-q), q(q-x) and r(r-p)​

Answer 1

$p(p - q) + q(q - x) + r(r - p) \\ = p {}^{2} - pq + q {}^{2} - xq + r {}^{2} - pr \\ = p {}^{2} + q {}^{2} + r {}^{2} - pq - xq - pr$