6(a-b)²-9(a+b)²

问题描述:

6(a-b)²-9(a+b)²

6(a-b)²-9(a+b)²
=6(a²+b²-2ab)-9(a²+b²+2ab)
=6a²+6b²-12ab-9a²-9b²-18ab
=-3a²-3b²-30ab