计算与求值(1)-3x2•2y+(2xy2)3÷(-2xy5)(2)已知x+y=1,求(x2-y2)2-2(x2+y2)的值.-数学

题目简介

计算与求值(1)-3x2•2y+(2xy2)3÷(-2xy5)(2)已知x+y=1,求(x2-y2)2-2(x2+y2)的值.-数学

题目详情

计算与求值
(1)-3x2•2y+(2xy23÷(-2xy5
(2)已知x+y=1,求(x2-y22-2(x2+y2)的值.
题型:解答题难度:中档来源:不详

答案

(1)-3x2•2y+(2xy2)3÷(-2xy5)
=-6x2y+8x3y6÷(-2xy5)
=-6x2y-4x2y
=-10x2y;

(2)(x2-y2)2-2(x2+y2)
=(x+y)2(x-y)2-2(x2+y2)
=(x-y)2-2(x2+y2)
=x2-2xy+y2-2x2-2y2
=-x2-2xy-y2
=-(x+y)2,
当x+y=1时,原式=-12=-1.

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