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For the Following Differential Equation, Find the General Solution:- Y Log Y D X − X D Y = 0

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Question

For the following differential equation, find the general solution:- `y log y dx − x dy = 0`

Sum
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Solution

We have,

\[y \log y\ dx - x\ dy = 0\]

\[ \Rightarrow y \log y dx = x dy\]

\[ \Rightarrow \frac{1}{x}dx = \frac{1}{y \log y}dy\]

\[ \Rightarrow \frac{1}{y \log y}dy = \frac{1}{x}dx\]

Integrating both sides, we get

\[\int\frac{1}{y \log y}dy = \int\frac{1}{x}dx . . . . . \left( 1 \right)\]

Putting log y = t

\[ \Rightarrow \frac{1}{y}dy = dt\]

Therefore (1) becomes

\[\int\frac{1}{t}dt = \int\frac{1}{x}dx\]

\[ \Rightarrow \log \left( t \right) = \log x + \log C\]

\[ \Rightarrow \log \left( \log y \right) = \log x + \log C\]

\[ \Rightarrow \log \left( \log y \right) = \log Cx\]

\[ \Rightarrow \log y = Cx\]

\[ \Rightarrow y = e^{Cx}\]

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Chapter 21: Differential Equations - Revision Exercise [Page 146]

APPEARS IN

R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 21 Differential Equations
Revision Exercise | Q 64.4 | Page 146

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