CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    The equation of smallest degree with real coefficients having\[2+3i\]as one of the roots, is:

    A)  \[{{x}^{2}}+4x+13=0\]

    B)         \[{{x}^{2}}+4x-13=0\]

    C)  \[{{x}^{2}}-4x+13=0\]

    D)         \[{{x}^{2}}-4x-13=0\]

    E) \[{{x}^{2}}+2x+13=0\]

    Correct Answer: C

    Solution :

    If one root is\[2+3i,\]then another root will be\[2-3i\]. \[\therefore \] Sum of roots \[=2+3i+2-3i=4\] and product of roots\[=(2+3i)\text{ }(2-3i)\] \[=4+9=13\] \[\therefore \]Required equation is \[{{x}^{2}}-(sum\text{ }of\text{ }roots)x+(product\text{ }of\text{ }roots)=0\] \[{{x}^{2}}-4x+13=0\]


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