P-[Q-2P-(P-Q)]
=P-[Q-2P-P+Q]
=P-2Q+3P
=4P-2Q
=4(a^2+3ab+d^2)-2(a^2-3ab+b^2)
=2(a^2+9ab-b^2)+4d^2
=2(a+5)(a-4)+4d^2