3a平方b+2ab+负3ab平方+负4a平方b+3ab
问题描述：
3a平方b+2ab+负3ab平方+负4a平方b+3ab
答
=3a²b+2ab+（-3ab²）+（-4a²b）+3ab
=3a²b+2ab-3ab²-4a²b+3ab
=-a²b+5ab