作业帮化简求值x/(x-1)-3/(x-1)(x+2)-1x=-（2/3）
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化简求值x/(x-1)-3/(x-1)(x+2)-1x=-（2/3）
化简求值
x/(x-1)-3/(x-1)(x+2)-1
x=-（2/3）
化简求值x/(x-1)-3/(x-1)(x+2)-1x=-（2/3）
x/(x-1)-3/(x-1)(x+2)-1
=x(x+2)/(x-1)(x+2)-3/(x-1)(x+2)-(x-1)(x+2)/(x-1)(x+2)
=[x(x+2)-3-(x-1)(x+2)]/(x-1)(x+2)
=[x^2+2x-3-(x-1)(x+2)]/(x-1)(x+2)
=[(x+3)(x-1)-(x-1)(x+2)]/(x-1)(x+2)
=(x-1)[(x+3)-(x+2)]/(x-1)(x+2)
=(x-1)(x+3-x-2)/(x-1)(x+2)
=(x-1)/(x-1)(x+2)
=1/(x+2)
=1/(-2/3+2)
=1/(4/3)
=3/4
想通分，把分母变成一样后，就好办了啊
3/40
1 x^2+2x+1 x^2-1
= --- - ----------- / -------
x+2 x+2 x-1
1 (x+1)^2 x-1
= --- - --------- * -------
x+2 x+2 x^2-1
1 ...
全部展开
1 x^2+2x+1 x^2-1
= --- - ----------- / -------
x+2 x+2 x-1
1 (x+1)^2 x-1
= --- - --------- * -------
x+2 x+2 x^2-1
1 (x+1)^2 x-1
= --- - -------- * ----------
x+2 x+2 (x-1)(x+1)
1 x+1
= --- - -----
x+2 x+2
1-(x+2)
= -------
x+2
因为x^2 = 4
所以x=±2
当x=+2时
1
本方程的解为 - ---
2
当x=-2时
无解！
收起
第一个分式分子分母乘（x-1）第三个分子分母乘(x-1)(x+2) 再分式相加 上面的分子是x(x-1)(x+2)-3-(x-1)(x+2) 拆开再因式分解得(x-1)(x+2)(x+3)和分母相约就可以了
x/(x-1)-3/(x-1)(x+2)-1
=x*(x+2)/[(x-1)(x+2)]-3/(x-1)(x+2)-1
=(x^2+2x-3)/(x-1)(x+2)-1
=(x+3)/(x+2)-1
=3/4
等于1吧....
通分
(x^2+2x-3)/(x-1)(x+2) -1
分子提出x-1消去 剩下的不写了