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Choose the correct option from the given alternatives : If y = andABdydxCacos(logx)andAd2ydx2+Bdydx+C = 0, then the values of A, B, C are - Mathematics and Statistics

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Question

Choose the correct option from the given alternatives :

If y = `a cos (logx) and "A"(d^2y)/(dx^2) + "B""dy"/"dx" + "C"` = 0, then the values of A, B, C are

Options

  • x2, – x, – y

  • x2, x, y

  • x2, x, – y

  • x2, –x, y

MCQ

Solution

x2, x, y
[Hint : y = a cos (log x)                       ...(1)

∴ `"dy"/"dx" = a[-sin(logx)] xx (1)/x`

∴ `x"dy"/"dx" = -asin(logx)`

∴ `x(d^2y)/(dx^2) + "dy"/"dx" = -acos(logx) xx (1)/x`

∴ `x(d^2y)/(dx^2) + "dy"/"dx"` = – y                          ...[By (1)]

∴ `x2(d^2y)/(dx^2) + x"dy"/"dx" + y` = 0

Comparing this with `"A"(d^2y)/(dx^2) + "B""dy"/"dx" + "C"` = 0, we get A = x2, B = x, C = y.

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Chapter 1: Differentiation - Miscellaneous Exercise 1 (I) [Page 63]

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