JCECE Engineering JCECE Engineering Solved Paper-2003

  • question_answer
    After second iteration of Newton-Raphson method, the positive root of equation \[{{x}^{2}}=3\](taking initial approximation\[\frac{3}{2}):\]

    A) \[3/2\]                                 

    B)  \[7/4\]

    C) \[97/56\]                            

    D) \[347/200\]

    Correct Answer: C

    Solution :

    Key Idea: The Newton-Raphson formula for the function\[f(x)\]is                 \[{{x}_{n+1}}={{x}_{n}}-\frac{f({{x}_{n}})}{f'({{x}_{n}})}\] Let          \[f(x)={{x}^{2}}-3\] On differentiating w.r.t. x, we get                 \[f'(x)={{x}^{2}}-3\] \[\therefore \]By using Newton-Raphson of first iteration.                 \[{{x}_{1}}={{x}_{0}}-\frac{f({{x}_{0}})}{f'({{x}_{0}})}\]                 \[=\frac{3}{2}-\frac{\frac{9}{4}-3}{2\times \frac{3}{2}}=\frac{3}{2}+\frac{1}{4}=\frac{7}{4}\] Second iteration is                 \[{{x}_{2}}={{x}_{1}}-\frac{f({{x}_{1}})}{f'({{x}_{1}})}\]                 \[=\frac{7}{4}-\frac{\frac{1}{16}}{\frac{7}{2}}=\frac{7}{4}-\frac{1}{56}\]                 \[=\frac{97}{56}\].


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