CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2003

  • question_answer
    If\[\alpha \]and\[\beta \]are the solutions of the quadratic equation\[a{{x}^{2}}+bx+c=0\]such that\[\beta ={{\alpha }^{1/3}},\]then:

    A)  \[{{(ac)}^{1/3}}+{{(ab)}^{1/3}}+c=0\]

    B)  \[{{({{a}^{3}}b)}^{1/4}}+{{(a{{b}^{3}})}^{1/4}}+c=0\]

    C)  \[{{({{a}^{3}}c)}^{1/4}}+{{(a{{c}^{3}})}^{1/4}}+b=0\]

    D)  \[{{({{a}^{4}}c)}^{1/3}}+{{(a{{c}^{4}})}^{1/3}}+b=0\]

    E)  \[{{({{a}^{3}}c)}^{1/4}}-{{(a{{c}^{3}})}^{1/4}}+b=0\]

    Correct Answer: C

    Solution :

    \[\because \]\[\alpha \]and\[\beta \]are the roots of equation \[a{{x}^{2}}+bx+c=0.\] \[\alpha +\beta =-\frac{b}{a}\]and \[\alpha \beta =\frac{c}{a}\] \[\Rightarrow \]               \[\alpha +{{\alpha }^{1/3}}=-\frac{b}{a}\]and\[{{\alpha }^{4/3}}=\frac{c}{a}\]                                                 \[(\because \beta ={{\alpha }^{1/3}})\] \[\Rightarrow \]               \[{{\left( \frac{c}{a} \right)}^{3/4}}+{{\left( \frac{c}{a} \right)}^{1/4}}=-\frac{b}{a}\] \[\Rightarrow \]               \[{{({{a}^{3}}c)}^{1/4}}+{{(a{{c}^{3}})}^{1/4}}=-\frac{b}{a}\]


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