相关2xy2x的文学知识

先化简,再求值:(2x+y)2+(x-y)(x+y)-5x(x-y),其中.

先化简,再求值:(2x+y)2+(x-y)(x+y)-5x(x-y),其中.

问题详情:先化简,再求值:(2x+y)2+(x-y)(x+y)-5x(x-y),其中.【回答】解:(2x+y)2+(x-y)(x+y)-5x(x-y)=4x2+4xy+y2+x2-y2-5x2+5xy=9xy,当x=+1,y=-1时,原式=9×(+1)×(-1)=9×(2-1)=9×1=9.知识点:乘法公式题型:解答题...