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    Question

    If 8x2 + y2 − 12x − 4xy + 9 =

    0, then the value of (14x − 5y) is :
    A 9 Correct Answer Incorrect Answer
    B 3 Correct Answer Incorrect Answer
    C 5 Correct Answer Incorrect Answer
    D 6 Correct Answer Incorrect Answer

    Solution

    8x²+y²-12x-4xy+9 = 0 8x²+y²-12x-4xy+9 = 0 (2x-y) ² + (2x-3) ² = 0 ∴ 2x-3 = 0 ⇒ x = 3/2 2x-y = 0 3-y = 0⇒ y= 3 ∴ (14x-5y) = 14× 3/2 − 5 × 3 = 21-15 = 6

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