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9th Class Mathematics Number System and its Operations Question Bank Number System

  • question_answer
    Which of the following is the value of a in \[\frac{\sqrt{\mathbf{5}}\mathbf{-}\sqrt{\mathbf{3}}}{\sqrt{\mathbf{5}}\mathbf{+}\sqrt{\mathbf{3}}}\mathbf{=a+b}\sqrt{\mathbf{15}}\]

    A)  2                                

    B)  -1            

    C)  -3                               

    D)  4

    Correct Answer: D

    Solution :

    (d): \[\frac{\sqrt{5}-\sqrt{3}}{\sqrt{5}+\sqrt{3}}\times \frac{\sqrt{5}-\sqrt{3}}{\sqrt{5}-\sqrt{3}}=\frac{{{\left( \sqrt{5}-\sqrt{3} \right)}^{2}}}{2}\] \[=\frac{8-2\sqrt{15}}{2}=4-\sqrt{25}\therefore a=4,b=-1\]


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