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( X + 2 ) D Y D X = X 2 + 3 X + 7

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Question

\[\left( x + 2 \right)\frac{dy}{dx} = x^2 + 3x + 7\]
Sum
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Solution

We have, 
\[\left( x + 2 \right)\frac{dy}{dx} = x^2 + 3x + 7\]
\[ \Rightarrow \frac{dy}{dx} = \frac{x^2 + 3x + 7}{x + 2}\]
\[ \Rightarrow dy = \left( \frac{x^2 + 3x + 7}{x + 2} \right)dx\]
Integrating both sides, we get
\[\int dy = \int\left( \frac{x^2 + 3x + 7}{x + 2} \right)dx\]
\[ \Rightarrow \int dy = \int\left( \frac{x^2 + 3x + 2 + 5}{x + 2} \right)dx\]
\[ \Rightarrow \int dy = \int\left[ \frac{\left( x + 2 \right)\left( x + 1 \right) + 5}{x + 2} \right]dx\]
\[ \Rightarrow \int dy = \int\left( x + 1 + \frac{5}{x + 2} \right)dx\]
\[ \Rightarrow y = \frac{x^2}{2} + x + 5 \log\left| x + 2 \right| + C\]
\[\text{ So, } y = \frac{x^2}{2} + x + 5 \log\left| x + 2 \right| +\text{C is defined for all } x \in R\text{ except }x = - 2 . \]
\[\text{Hence, }y = \frac{x^2}{2} + x + 5 \log\left| x + 2 \right| + \text{C, where }x \in R - \left\{ 2 \right\},\text{ is the solution to the given differential equation.}\]

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Chapter 21: Differential Equations - Exercise 22.05 [Page 34]

APPEARS IN

R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 21 Differential Equations
Exercise 22.05 | Q 6 | Page 34

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