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Verify y = log x + c is the solution of differential equation xd2ydx2+dydx = 0

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Question

Verify y = log x + c is the solution of differential equation `x ("d"^2y)/("d"x^2) + ("d"y)/("d"x)` = 0

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Solution

y = log x + c

Differentiating w.r.t. x, we get

`("d"y)/("d"x) = 1/x`

∴ `x ("d"y)/("d"x)` = 1

Again, differentiating w.r.t. x, we get

`x ("d"^2y)/("d"x^2) + ("d"y)/("d"x) xx 1` = 0

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

∴ y = log x + c is the solution of `x ("d"^2y)/("d"x^2) + ("d"y)/("d"x)` = 0

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Chapter 2.6: Differential Equations - Attempt the following questions II

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