Question

    If 4x2 + y2 = 40 and xy = 6, then

    find the value of 2x + y.
    A 6 Correct Answer Incorrect Answer
    B 8 Correct Answer Incorrect Answer
    C 5 Correct Answer Incorrect Answer
    D 4 Correct Answer Incorrect Answer

    Solution

    ATQ, (2x+y)2 = (2x)2 + y2 + (2 × 2x × y) = (2x+y)2 = (4x2 + y2) + 4xy = (2x + y)2 = 40 + 4 × 6 ⇒ (2x + y)2 = 64 = 2x + y = ±64    = 2x + y = ±8

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