若a的平方+3ab=4 5ab+2b^ =2 则2a^减9ab减6b^值为大神们帮帮忙
问题描述：
若a的平方+3ab=4 5ab+2b^ =2 则2a^减9ab减6b^值为大神们帮帮忙
答
(2a+5b-3ab)-(a+6b-ab)-(2ab+2b-2a) =2a+5b-3ab-a-6b+ab-2ab-2b+2a =3a-3b-4ab =3(a-b)-4ab =12-12 =0