(3a²-ab+7）-（-4a²+2ab+7）=?

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

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

(3a²-ab+7)-(-4a²+2ab+7)
=3a²-ab+7+4a²-2ab-7
=(3+4)a²+(-1-2)ab+(7-7)
=7a²-3ab
=a(7a-3b)

3a²-ab+7）-（-4a²+2ab+7）
=3a^2-ab+7+4a^2-2ab-7
=7a^2-3ab
=a(7a-3b)