230问答网 > 已知：x^3+3x-8=0,求代数式1⼀x-2乘以x^2-4x+4⼀x+1 -x-1⼀x+2

已知：x^3+3x-8=0,求代数式1⼀x-2乘以x^2-4x+4⼀x+1 -x-1⼀x+2

2024-12-13 12:29:42

推荐回答（3个）

回答1：

应该是x^2+3x-8=0吧？
所以x^2+3x=8
1/(x-2)乘以(x^2-4x+4)/(x+1) -(x-1)/(x+2)=-3/[(x+1)(x+2)]=-3/(x^2+3x+3)=-3/(8+3)=-3/11

回答2：

请把你的题目重新写一下，把括号加上

回答3：

x^2+3x-8=0
x^2+3x=8

1/(x-2) * (x^2-4x+4)/(x+1) -(x-1)/(x+2)
= 1/(x-2) * (x-2)^2/(x+1) -(x-1)/(x+2)
= (x-2)/(x+1) - (x-1)/(x+2)
= [ (x-2)(x+2) - (x-1)(x+1) ] / [ (x+1)(x+2)]
= [ x^2-4-x^2+1] / [ (x+1)(x+2)]
= -3 / (x^2+3x+2)
= -3 / (8+2)
= -3/10