RAJASTHAN ­ PET Rajasthan PET Solved Paper-2007

  • question_answer
    If\[{{x}_{0}}=1\]is to find the real roots of the equation \[{{x}^{2}}-x=2\]by Newton-Raphson's method then the value of\[{{x}_{2}}\]is

    A)  9/15             

    B)  3

    C)  11/5            

    D)  19/5

    Correct Answer: C

    Solution :

     Given,  \[f(x)={{x}^{2}}-x-2\] \[\Rightarrow \] \[f'(x)=2x-1\] By Newton, Raphson method, \[{{x}_{1}}={{x}_{0}}-\frac{f({{x}_{0}})}{f'({{x}_{0}})}\] \[\Rightarrow \] \[{{x}_{1}}=1-\frac{f(1)}{f'(1)}\] \[\Rightarrow \] \[{{x}_{1}}=1-\frac{(1-1-2)}{2-1}=3\] and \[{{x}_{2}}={{x}_{1}}-\frac{f({{x}_{1}})}{f'({{x}_{1}})}\] \[\Rightarrow \] \[x=3-\frac{(9-3-2)}{(2\times 3-1)}\] \[\Rightarrow \] \[{{x}_{2}}=\frac{11}{5}\]


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