证明:代数式[(x+y)(x-y)-(x+y)^2-2y(x-y)-2xy]/xy 的值为x,y的值无关 解方程 (x+
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证明:代数式[(x+y)(x-y)-(x+y)^2-2y(x-y)-2xy]/xy 的值为x,y的值无关 解方程 (x+1)^5/(-1-x)^4=3x+7
一定要100%正确阿.
一定要100%正确阿.
[(x+y)(x-y)-(x+y)^2-2y(x-y)-2xy]/xy
={(x+y)[(x-y)-(x+y)]-2y(x-y)-2xy}/xy
={(x+y)[(x-y-x-y)]-2y(x-y)-2xy}/xy
={-2y(x+y)-2y(x-y)-2xy}/xy
={-2y[(x+y)+(x-y)]-2xy}/xy
={-2y[x+y+x-y]-2xy}/xy
={-4xy-2xy}/xy
=-6xy/xy
=-6
所以代数式[(x+y)(x-y)-(x+y)^2-2y(x-y)-2xy]/xy 的值为x,y的值无关
(x+1)^5/(-1-x)^4=3x+7
(x+1)^5/(1+x)^4=3x+7
x+1=3x+7
3x-x=1-7
2x=-6
x=-3
经检验x=-3是方程的解
={(x+y)[(x-y)-(x+y)]-2y(x-y)-2xy}/xy
={(x+y)[(x-y-x-y)]-2y(x-y)-2xy}/xy
={-2y(x+y)-2y(x-y)-2xy}/xy
={-2y[(x+y)+(x-y)]-2xy}/xy
={-2y[x+y+x-y]-2xy}/xy
={-4xy-2xy}/xy
=-6xy/xy
=-6
所以代数式[(x+y)(x-y)-(x+y)^2-2y(x-y)-2xy]/xy 的值为x,y的值无关
(x+1)^5/(-1-x)^4=3x+7
(x+1)^5/(1+x)^4=3x+7
x+1=3x+7
3x-x=1-7
2x=-6
x=-3
经检验x=-3是方程的解
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