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InEquality

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shekhar.kataria Really wants to Beat The GMAT! Default Avatar
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InEquality Post Tue Mar 13, 2012 3:24 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Find the solution to the inequality :
    2x+5
    ------------ <3
    |x| +1

    1.x < -2/5 or x > 1
    2.x < -1 or x > 2/5
    3.x < -2/5 or x > 2
    4.x > -2/5 or x < 2
    5.x > 1 or x < -1

    Pleas tell what is the problem within my approach :-

    I am considering two secanarios, one is X>=0 and other is X<0; X can not be zero because if X=0 , inequality doesn't stand correct.

    FOR X>0 ;
    2x+5
    ------------ <3
    x +1
    Solving this will give X>2

    For X<0 i.e value of X as negative

    -2x+5
    ------------ <3
    x +1

    Doubt 1:- IS the above expression true when X<0;
    Dount 2:- If yes, then after solving this i am getting X>2/5, which is not a solution of this.

    Where i am wrong in getting concept of inequality. Please explain

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    killer1387 GMAT Destroyer! Default Avatar
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    Post Tue Mar 13, 2012 4:26 am
    shekhar.kataria wrote:
    Find the solution to the inequality :
    2x+5
    ------------ <3
    |x| +1

    1.x < -2/5 or x > 1
    2.x < -1 or x > 2/5
    3.x < -2/5 or x > 2
    4.x > -2/5 or x < 2
    5.x > 1 or x < -1

    Pleas tell what is the problem within my approach :-

    I am considering two secanarios, one is X>=0 and other is X<0; X can not be zero because if X=0 , inequality doesn't stand correct.

    FOR X>0 ;
    2x+5
    ------------ <3
    x +1
    Solving this will give X>2

    For X<0 i.e value of X as negative

    -2x+5
    ------------ <3
    x +1


    should be
    2x+5
    ------------ <3
    -x +1

    Doubt 1:- IS the above expression true when X<0;
    Dount 2:- If yes, then after solving this i am getting X>2/5, which is not a solution of this.

    Where i am wrong in getting concept of inequality. Please explain
    here 3 is correct.
    my approach:

    2x+5 <3*(|x| +1 ) (|x| +1 is positive hence no change of sign)

    i.e. 3|x|-2x>2
    for x>0;
    x>2

    for x<0
    x< -2/5

    hence C.

    P.S.: PLease check the part in bold in your solution.

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