已知B-A=4,则2A²-4AB+2B²-13的值为
问题描述:
已知B-A=4,则2A²-4AB+2B²-13的值为
答
=2(a^2-2ab+b^2)-13
=2(a-b)^2-13
=2(b-a)^2-13
=2*4^2-13
=19
答
2A²-4AB+2B²-13
=2﹙A²-2AB+B²﹚-13
=2﹙B-A﹚²-13
=2×16-13
=19