Railways R.R.C. (Patna) Solved Paper Held on 1st Shift 2-11-2014

  • question_answer
    If \[{{2}^{a}}+{{3}^{b}}=17\]and \[{{2}^{a+2}}-{{3}^{b+1}}=5\], then-

    A) a=2, 6 = 3                   

    B) \[a=-2\], c=3

    C) a=2, \[b=-3~~\]

    D) a=3, b=2

    Correct Answer: D

    Solution :

    If \[{{2}^{a}}+{{3}^{b}}=17\] \[{{2}^{a}}+{{3}^{b}}=8+9\] \[={{2}^{3}}+{{3}^{2}}\] Then,    \[a=3\] and       \[b=2\] and       \[{{2}^{a+2}}-{{3}^{b+1}}=5\] \[4\times {{2}^{a}}-3\times {{3}^{b}}=32-27\] \[=4\times {{2}^{3}}-3\times {{3}^{2}}\]


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