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(y-x)/(x+z-2y)(x+y-2z)+(z-y)(x-y)/(x+y-2z)(y+z-2x)+(x-z)(y-z

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/10 06:40:40
(y-x)/(x+z-2y)(x+y-2z)+(z-y)(x-y)/(x+y-2z)(y+z-2x)+(x-z)(y-z)/(y+z-2x)(x+z-2y)的值
我已经做到这了:设(X-Y)为a (Z-Y)为b (Z-X)为c
则原题= (-a*-c)/-(a+b)(b+c)+ab/-(c+b)(a+c)+c*-b/(-a+c)(a+b)
∑是循环和
例如
∑a=a+b+c
∑a^2=a^2+b^2+c^2
∑(z-y)(x-y)/(x+y-2z)(y+z-2x)
=∑(z-y)(x-y)(x+z-2y)/(x+y-2z)(y+z-2x)(x+z-2y)
=[1/(x+y-2z)(y+z-2x)(x+z-2y)]∑(z-y)(x-y)(x+z-2y)
你的设法不科学,丧失了轮转对称性!
x-y=a
y-z=b
z-x=c
a+b+c=0
∑(z-y)(x-y)(x+z-2y)
=∑(z-y)(x-y)(x-y)+∑(z-y)(x-y)(z-y)
=-∑aab+∑bba
=(a-b)(b-c)(c-a)
1/(x+y-2z)(y+z-2x)(x+z-2y)
=1/(b-c)(c-a)(a-b)
所求=1