Question
Solve the following differential equation
$\text{xy}(\text{y}+1)\text{dy}=(\text{x}^2+1)\text{dx}$

Answer

 We have

$\text{xy}(\text{y}+1)\text{dy}=(\text{x}^2+1)\text{dx}$

$\Rightarrow\{\text{y}(\text{y}+1)\}\text{dy}=\frac{\text{x}^2+1}{\text{x}}\ \text{dx}$

$\Rightarrow(\text{y}^2+\text{y})\text{dy}=\Big(\text{x}+\frac{1}{\text{x}}\Big)\text{dx}$

Integrating both sides, we get

$\int(\text{y}^2+\text{y})\text{dy}=\int\Big(\text{x}+\frac{1}{\text{x}}\Big)\text{dx}$

$=\int\text{y}^2\text{dy}+\int\text{y dy}=\int\text{x dx}+\int\frac{1}{\text{x}}\text{ dx}$

$\Rightarrow\frac{\text{y}^3}{3}+\frac{\text{y}^3}{2}=\frac{\text{x}^2}{2}+\log|\text{x}|+\text{C}$

Hence,
 $\frac{\text{y}^3}{3}+\frac{\text{y}^3}{2}=\frac{\text{x}^2}{2}+\log|\text{x}|+\text{C}$ is the required solution. 

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