(3a的2次幂-ab+7)-(-4a的2次幂+2ab+7)

问题描述:

(3a的2次幂-ab+7)-(-4a的2次幂+2ab+7)

原式=3a²-ab+7+4a²-2ab-7
=(3a²+4a²)-(ab+2ab+(7-7)
=7a²-3ab