Question

(x-2y)2+(x+2y)(x-2y)-(x-3y)(x-y)计算结果是什么?x等于-4,y等于0.5代入后是多少第一

Answer 1

(x-2y)²+(x+2y)(x-2y)-(x-3y)(x-y)=x²-4xy+4y²+x²-4y²-x²+4xy-3y²=x²-3y²x=-4,y=0.5代入原式=（-4）²-3（0.5）²=16-0.75=15.25