Maths Question

2013-02-08 5:35 am
Solve the inequalities

-2< (x-1/x+2) <2

回答 (1)

2013-02-08 6:05 am
✔ 最佳答案
Solvethe inequalities
-2< (x-1)/(x+2) <2
Sol
(1) -2<(x-1)/(x+2)
(x-1)/(x+2)+2>0
[(x-1)+2(x+2)]/(x+2)>0
(3x+3)/(x+2)>0
(x+1)(x+2)>0
x<-2 or x>-1………………..
(2) (x-1)/(x+2)<2
(x-1)/(x+2)-2<0
[(x-1)-2(x+2)]/(x+2)0
(-x-5)/(x+2)<0
(x+2)(x+5)>0
x<-2 or x>-5……………….
<─────────O O─────>
<───O     O───────────>
   -5    -2    -1
────*─────*─────*──────
So
x<-5 or x>-1

or-2< (x-1)/(x+2) <2
|(x-1)/(x+2)|<2
(x-1)^2/(x+2)^2<4
(x-1)^2<4(x+2)^2
4(x+2)^2-(x-1)^2>0
(2x+4)^2-(x-1)^2>0
(2x+4+x-1)(2x+4-x+1)>0
(3x+3)(x+5)>0
(x+1)(x+5)>0
x<-5 or x>-1




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