CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    If\[|2x-3|<|x+5|,\]then\[x\]lies in the interval

    A)  \[(-3,5)\]                            

    B)  \[(5,9)\]

    C)  \[\left( -\frac{2}{3},8 \right)\]   

    D)         \[\left( -8,\frac{2}{3} \right)\]

    E)  \[\left( -5,\frac{2}{3} \right)\]

    Correct Answer: C

    Solution :

    \[|2x-3|<|x+5|\] \[\Rightarrow \]\[\pm (2x-3)<\pm (x+5)\]                           ?.. (i) First we take positive sign and negative sign on both sides, \[\Rightarrow \]               \[2x-3<x+5\] \[\Rightarrow \]               \[x<8\]                                                 ?.(ii)                 \[-(2x-3)<-(x+5)\] \[\Rightarrow \]               \[2x-3>x+5\] \[\Rightarrow \]               \[x>8\]                                                 ?.(iii) Now, we take negative sign in RHS and positive in LHS, \[\Rightarrow \]               \[2x-3<-x-5\] \[\Rightarrow \]               \[3x<-2\] \[\Rightarrow \]               \[x<-\frac{2}{3}\]                                             ?.. (iv) and we take negative sign LHS and positive in RHS, \[\Rightarrow \]               \[-(2x-3)<x+5\] \[\Rightarrow \]               \[-2x+3<x+5\] \[\Rightarrow \]               \[-2<3x\] \[\Rightarrow \]               \[-2/3<x\]                           ?.(v) From Eqs. (ii) and (v), \[-2/3<x<8\] \[\Rightarrow \]               \[x\in (-2/3,8)\] From Eqs. (iii) and (iv),                 \[x\in (-\infty ,-2/3)\cup (8,\infty )\]


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