Question

2(ax+by)*(by-ax)-(ax+by)²-(by-ax)²,其中a=-3,x=2分之1

Answer 1

2(ax+by)*(by-ax)-(ax+by)2-(by-ax)2用公式a2-2ab+b^2=(a-b)^2即可

=-{（ax+by)2-2(ax+by)*(by-ax)+（by-ax)2}

=-（ax+by-by+ax）^2

=-4（ax)^2=-9