SSC Sample Paper SSC-CGL TIER - I Sample Test Paper-9

  • question_answer
    If 1 he roots of the equation \[{{x}^{2}}+2(3a+5)x+2(9{{a}^{2}}+25)=0\]are equal, then the value of a is:

    A) 1                                 

    B) 2

    C) \[\frac{2}{3}\]                          

    D) \[\frac{1}{3}\]

    Correct Answer: D

    Solution :

    \[\therefore \] The roots of \[{{x}^{2}}+2(3a+5)x+2(9{{a}^{2}}+25)=0\] are equal. \[\Rightarrow \]\[{{[2(3a+5)]}^{2}}-4\times 1\times 2\left( 9{{a}^{2}}+25 \right)\] \[\Rightarrow \]\[4\left( 9{{a}^{2}}+30a+25 \right)-8\left( 9{{a}^{2}}+25 \right)=0\] \[\Rightarrow \]\[-9{{a}^{2}}+30a-25=0\] \[\Rightarrow \]\[9{{a}^{2}}-30a+25=0\] \[\Rightarrow \,\,\,\,\,\,\,\,{{\left( 3a-5 \right)}^{2}}=0\Rightarrow a=\]\[\frac{5}{3}\]


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