a²-2ab=3 b²-ab=4 求-2a²+ab+3b²

问题描述:

a²-2ab=3 b²-ab=4 求-2a²+ab+3b²

-2a²+ab+3b² = -2(a²-2ab)+3b²-3ab = -2x3 + 3x4 = 6