JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Square root, Representation and Logarithm of complex numbers

  • question_answer
    If \[z=\frac{7-i}{3-4i}\] then \[{{z}^{14}}=\] [Kerala (Engg.) 2005]

    A) \[{{2}^{7}}\]

    B) \[{{2}^{7}}i\]

    C) \[{{2}^{14}}i\]

    D) \[-{{2}^{7}}i\]

    E) \[-{{2}^{14}}\]

    Correct Answer: D

    Solution :

    \[z=\frac{7-i}{3-4i}\times \frac{3+4i}{3+4i}\]=\[\frac{21+25i+4}{16+9}=\frac{25\,(1+i)}{25}\] = \[(1+i)\] \[{{z}^{14}}={{(1+i)}^{14}}={{[{{(1+i)}^{2}}]}^{7}}\]= \[{{(2i)}^{7}}={{2}^{7}}{{i}^{7}}=-{{2}^{7}}i\].


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