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Find an implicit formula satisfied by solutions of y′ = (y-1)(y-2)

Assume solutions of the equation

    \[ y' = (y-1)(y-2) \]

exist and find an implicit formula satisfied by these solutions.


This is a separable first order equation. We compute

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

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