作业帮{80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 怎么解( ⊙ o ⊙ {80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 快 急
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{80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 怎么解( ⊙ o ⊙ {80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 快 急
{80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 怎么解( ⊙ o ⊙
{80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 快 急
{80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 怎么解( ⊙ o ⊙ {80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 快 急
这道题的思路很简单,就是一个二元方程组.首先把两个方程的左边项分别通分,两个方程的分母（x²-y²）和右边项（7）都一样,那么他们的分子也相等,也即122x-38y=110x+30y,由此把y用x表示,可以得到y=3x/17,把这一式子带到前面任意一个方程中,就是一个关于x的一元方程了,以代到第一个方程中为例,可以得到式子为80/(x+3x/17)+42/(x-3x/17)=7,由此解出x=17,所以把x=17代到y=3x/17中,可以解出y=3.
1/(x+y)=1/20 1/(x-y)=1/14
x+y=20 x-y=14
x=17 y=3
把1/(x+y),1/(x-y)看成整体
可得 1/(x+y)=1/20 1/(x-y)=1/14
所以 x+y=20 x-y=14
x=17 y=3
把x+y和x-y看成两个整体，设x+y=a，x-y=b
算出ab为多少，然后再算x、y
{(x,y) |x|+|y|
x>y?x:y
x+80%y=42 y-x=12
{80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 怎么解( ⊙ o ⊙ {80/(x+y) +42/(x-y) =7 40/(x+y) +70/(x-y) =7 快 急
解方程组80/x+y + 42/x-y=7 40/x+y + 7/x-y=7非常感谢!
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