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2 ( Y + 3 ) − X Y D Y D X = 0 , Y(1) = −2

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Question

\[2\left( y + 3 \right) - xy\frac{dy}{dx} = 0\], y(1) = −2
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Solution

\[2\left( y + 3 \right) - xy\frac{dy}{dx} = 0\]
\[\Rightarrow 2\left( y + 3 \right) = xy\frac{dy}{dx}\]
\[ \Rightarrow \frac{2}{x}dx = \frac{y}{y + 3}dy\]
\[ \Rightarrow \frac{2}{x}dx = \frac{y + 3 - 3}{y + 3}dy\]
\[ \Rightarrow \frac{2}{x}dx = \left( 1 - \frac{3}{y + 3} \right)dy\]
\[ \Rightarrow \int\frac{2}{x}dx = \int\left( 1 - \frac{3}{y + 3} \right)dy\]
\[ \Rightarrow 2\log x = y - 3\log\left| y + 3 \right| + C\]
\[ \Rightarrow \log x^2 + \log\left| \left( y + 3 \right)^3 \right| = y + C\]
\[ \Rightarrow \log\left| \left( x^2 \right) \left( y + 3 \right)^3 \right| = y + C . . . . . \left( 1 \right)\]
\[\Rightarrow \log\left| \left( 1 \right)^2 \left( - 2 + 3 \right)^3 \right| = - 2 + C\]
\[ \Rightarrow C = 2\]
Substituting the value of C in (1), we get
\[\log\left| \left( x^2 \right) \left( y + 3 \right)^3 \right| = y + 2\]
\[ \Rightarrow \left( x^2 \right) \left( y + 3 \right)^3 = e^{y + 2} \]
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Chapter 21: Differential Equations - Exercise 22.07 [Page 56]

APPEARS IN

R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 21 Differential Equations
Exercise 22.07 | Q 45.9 | Page 56

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