21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)结果为(x+y)/(x-y)=3求过程!

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21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)结果为(x+y)/(x-y)=3求过程!
21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)
结果为(x+y)/(x-y)=3
求过程!

21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)结果为(x+y)/(x-y)=3求过程!
21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)
21/(x+y)-12/(x+y)=7/(x-y)-4/(x-y)
9/(x+y)=3/(x-y)
(x+y)/(x-y)=9/3=3

21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)
移项后得：
21/(x+y)-12/(x+y)= 7/(x-y) -4/(x-y)
即：9/(x+y)= 3/(x-y)
因此：(x+y)/(x-y)=3

21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)
21/(x+y)-12/(x+y)=7/(x-y)-4/(x-y)
9/(x+y)=3/(x-y)
(x+y)/(x-y)=9/3=3

21/(x+y)-12/(x+y)=7/(x-y)-4/(x-y)
9/(x+y)=3/(x-y)
3(x+y)=9(x-y)
(x+y)/(x-y)=3

21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)
两边同时乘以(x+y)(x-y),得
21(x-y)+4(x+y)=12(x-y)+7(x+y)
21x-21y+4x+4y=12x-12y+7x+7y
25x-17y=19x-5y
25x-19x=17y-5y
6x=12y
x=2y
所以：
(x+y)/(x-y)=(2y+y)/(2y-y)=3y/y=3
证毕

21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)
9/(x+y)=3/(x-y)
3=(x+y)(x-y)

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