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Find an implicit formula satisfied by solutions of (x + 1) y′ + y2 = 0

Assume solutions of the equation

    \[ (x+1)y' + y^2 = 0 \]

exist and find an implicit formula satisfied by these solutions.


This is a separable first order equation. We compute

    \begin{align*}  (x+1)y' + y^2 = 0 && \implies && y' \left( \frac{1}{y^2} \right) &= \frac{-1}{x+1} \\[9pt]  && \implies && \int \frac{1}{y^2} \, dy &= -\int \frac{1}{x+1} \, dx \\[9pt]  && \implies && -\frac{1}{y} &= -\log |x+1| + C \\[9pt]  && \implies && y \big( \log |x+1| + C \big) &= 1. \end{align*}

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