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If `log_(y) x + log_(x) y = 2, x^(2)+y = 12` , then the value of xy isA. 9B. 12C. 15D. 21 |
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Answer» Correct Answer - A Let ` t=log_(y) x(x, y gt 0, and ne 1)," then " t+1/t = 2 or (t-1)^(2) = 0` ` :. T = log_(y) x = 1 , i.e., x = y `.We get ` x^(2) + x - 12 = 0 x = -4, 3`. x = 3 only (-4 rejected) ` :. Y = 3`, ` :. X = 9` |
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