New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    Suppose, (√(5a+9) )+ (√(5a-9)) = 3(2+√2), then

    √(10a+9) will be equal to?
    A 21√7 Correct Answer Incorrect Answer
    B 3√7 Correct Answer Incorrect Answer
    C 5√7 Correct Answer Incorrect Answer
    D 2√7 Correct Answer Incorrect Answer

    Solution

    Given,

    Set x = √(5a+9 and y = √(5a-9,

    Giving x+y = 3(2+√2)

    Square both sides, we get = (x+y)2 = 54+36√2.

    By using x2 + y2 = 10a

    On solving for 10a = 54,

    So, 10a+9 = 63

    Hence, √(10a+9) = √63 = 3√7

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