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Railways Sample Paper RRB (Group D) Sample Test Paper-7

  • question_answer
    If a=11 and b=9, then the value of\[\left( \frac{{{a}^{2}}+{{b}^{2}}+ab}{{{a}^{3}}-\,{{b}^{3}}} \right)\]is

    A)  \[\frac{1}{2}\] 

    B)  2

    C)  \[\frac{1}{20}\]            

    D)  20

    Correct Answer: A

    Solution :

    [a] \[\frac{{{a}^{2}}+{{b}^{2}}+ab}{{{a}^{3}}-\,{{b}^{3}}}\] \[=\frac{{{a}^{2}}+{{b}^{2}}=ab}{(a-b)\,\,({{a}^{2}}+{{b}^{2}}+ab)}=\frac{1}{a-b}=\frac{1}{11-9}=\frac{1}{2}\]


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