CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    If\[\frac{{{a}^{n+1}}+{{b}^{n+1}}}{{{a}^{n}}+{{b}^{n}}}\]the arithmetic mean between a  and b, then n is equal to:

    A)  2        

    B)                                         \[-2\]                   

    C)         0                                            

    D)         1

    E)         \[-1\]

    Correct Answer: C

    Solution :

    AM of a and b is\[\frac{a+b}{2}\]. \[\Rightarrow \]               \[\frac{{{a}^{n+1}}+{{b}^{n+1}}}{{{a}^{n}}+{{b}^{n}}}=\frac{a+b}{2}\] \[\Rightarrow \] \[2({{a}^{n+1}}+{{b}^{n+1}})=({{a}^{n}}+{{b}^{n}})(a+b)\] \[\Rightarrow \] \[2{{a}^{n+1}}+2{{b}^{n+1}}={{a}^{n+1}}+{{a}^{n}}b\]\[+{{b}^{n}}a+{{b}^{n+1}}\] \[\Rightarrow \]               \[{{a}^{n+1}}+{{b}^{n+1}}={{a}^{n}}b+{{b}^{n}}a\] \[\Rightarrow \]               \[{{a}^{n}}(a-b)={{b}^{n}}(a-b)\] \[\Rightarrow \]               \[{{a}^{n}}={{b}^{n}}\] \[\Rightarrow \]               \[\frac{{{a}^{n}}}{{{b}^{n}}}=1\Rightarrow {{\left( \frac{a}{b} \right)}^{n}}={{\left( \frac{a}{b} \right)}^{0}}\] \[\Rightarrow \]               \[n=0\]


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