Solving the inequality 3/(|x+1|-1)+2/x<1

  • Thread starter Thread starter XJellieBX
  • Start date Start date
  • Tags Tags
    Inequalities
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
2 replies · 2K views
XJellieBX
Messages
39
Reaction score
0
Problem:
[tex]\frac{3}{|x+1|-1}[/tex]+[tex]\frac{2}{x}[/tex]<1

My Solution:
There are 2 cases:
1) x[tex]\geq0[/tex],[tex]\frac{3}{x+1-1}[/tex]+[tex]\frac{2}{x}[/tex]<1
[tex]\frac{3}{x}[/tex]+[tex]\frac{2}{x}[/tex]<1
And you end up with... x>5.

2) x<0, [tex]\frac{3}{-x-1-1}[/tex]+[tex]\frac{2}{x}[/tex]<1
[tex]\frac{3x-2x-4}{-x^{2}-2x}[/tex]<1
... a few reductions later...
[tex]x^{2}[/tex]+3x-4>0
And the solution set for this case is, -4>x>1

My Question:
Is there something I'm missing or something else I need to do?
 
Physics news on Phys.org
(edited: incorrect response)
 
Last edited:
"-4 > x> 1" implies -4> 1! x2+ 3x- 4= (x+ 4)(x- 1)> 0 if and only if the two factors are of the same sign. x+4> 0, x- 1> 0 give x> -4 and x> 1 which are both satisfied for x> 1. x+4< 0, x-1< 0 give x< -4, x< 1 which are both satisfied for x< -4.
x2+ 3x- 4> 0 for x< -4 OR x> 1.