10th Class Mathematics Related to Competitive Exam Question Bank Quadratic Inequation

  • question_answer
    The set of values for which \[{{x}^{3}}-1\ge x-{{x}^{2}}\] holds true is:

    A)  \[x\ge 0\]                      

    B)  \[x\le 0\]

    C)  \[x\ge 1\]

    D)  \[-1\le x\le 1\]

    Correct Answer: C

    Solution :

    (c): \[{{x}^{3}}-1\ge x-{{x}^{2}}\Rightarrow {{x}^{3}}+{{x}^{2}}-x-1\ge 0\] \[\Rightarrow {{x}^{2}}(x+1)-1(x+1)\ge 0\] \[\Rightarrow \left( {{x}^{2}}-1 \right)\left( x+1 \right)\ge 0\] \[\Rightarrow \left( x-1 \right){{\left( x+1 \right)}^{2}}\ge 0\Rightarrow x\ge 1\]                    


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