JEE Main & Advanced Mathematics Sequence & Series Question Bank Self Evaluation Test - Sequences and Series

  • question_answer
    If a, b, c are the sides of a triangle, then the minimum value of \[\frac{a}{b+c-a}+\frac{b}{c+a-b}+\]\[\frac{c}{a+b-c}\] is equal to

    A) 3

    B) 6    

    C) 9

    D) 12

    Correct Answer: A

    Solution :

    [a] Given expression is \[\frac{1}{2}\sum{\frac{2a}{b+c-a}}\] \[=\frac{1}{2}\sum{\left( \frac{2a}{b+c-a}+1 \right)}-\frac{3}{2}=\frac{1}{2}(a+b+c)\]             \[\sum{\frac{1}{b+c-a}}-\frac{3}{2}\] Now, as \[(a+b+c)=\Sigma (b+c-a)\] Applying \[A.M.\ge H.M.\] Minimum value of the expression \[=\frac{1}{2}\times 9-\frac{3}{2}=3.\]


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