$$ \frac{d}{dx}[(3x+1)\frac{du}{dx}] = 0 $$
Hint, expanding the derivative cannot solve it. I'm stuck.
Find general solution of differential equation
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ordinary-differential-equations
1 Answers
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Hint: Observe \begin{align} (3x+1)\frac{du}{dx} = C \end{align} for some constant $C$. Hence it follows \begin{align} \frac{du}{dx} = \frac{C}{3x+1}. \end{align}