化简：3a²-[7a-3(4a-3)-2a²]
问题描述：
化简：3a²-[7a-3(4a-3)-2a²]
答
3a²-[7a-3(4a-3)-2a²]
=3a²-(7a-12a+9-2a²)
=3a²+2a²+5a-9
=5a²+5a-9