JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Solution of quadratic equations and Nature of roots

  • question_answer
    The equation\[{{e}^{x}}-x-1=0\] has      [Kurukshetra CEE 1998]

    A) Only one real root \[x=0\]

    B) At least two real roots

    C) Exactly two real roots

    D) Infinitely many real roots

    Correct Answer: A

    Solution :

    \[{{e}^{x}}=x+1\Rightarrow 1+\frac{x}{1!}+\frac{{{x}^{2}}}{2!}+......=x+1\] Þ \[\frac{{{x}^{2}}}{2!}+\frac{{{x}^{3}}}{3!}+......=0\] \[{{x}^{2}}=0,{{x}^{3}}=0,\]......\[{{x}^{n}}=0\] Hence, \[x=0\]only one real root. Trick: Check the equation with options then only option (a) satisfies the equation.


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