BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    The equation\[{{x}^{3}}-3x+4=0\] has only one real root. What is its first approximate value as obtained by the method of false position in\[(-3,-2)?\]

    A) \[-2.125\]           

    B) \[2.125\]             

    C)        \[-2.812\]         

    D)        \[~2.812\]

    Correct Answer: A

    Solution :

    We know that, the first approximation by the method of false position is \[{{x}_{2}}={{x}_{0}}-\frac{{{x}_{1}}-{{x}_{0}}}{f({{x}_{1}})-f({{x}_{0}})}f({{x}_{0}})\] where \[{{x}_{0}}=-3,\,{{x}_{1}}=-2,\] \[f(x)={{x}^{3}}-3x+4\]                 \[\therefore \] \[f({{x}_{0}})=f(-3)=-27+9+4=-14\]                 \[f({{x}_{1}})=f(-2)=-8+6+4=2\]                 Thus,     \[{{x}_{2}}=-3-\frac{1}{16}.(-14)\]                 \[\Rightarrow \]               \[{{x}_{3}}=-3+\frac{7}{8}\]                 \[\Rightarrow \]               \[{{x}_{2}}=-\frac{17}{8}\]                 \[\Rightarrow \]               \[{{x}_{2}}=-2.125\]


You need to login to perform this action.
You will be redirected in 3 sec spinner