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.
题型:解答题难度:一般来源:不详
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. |
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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