Problem 148
Easy Exact Equations

Find the general and singular solutions (if any) of…

Find the general and singular solutions (if any) of $(y')^2-y^2=0$.

Explanation of Method

Factor into two linear equations $y'=\pm y$ and solve each; then apply the $p$-discriminant test to check for a singular solution, and verify that the candidate it produces is already contained in the general solution.

Step 1: Factor and solve both branches

$(y'-y)(y'+y)=0$ gives $y'=y$ or $y'=-y$, with solutions $y=C_1e^{x}$ and $y=C_2e^{-x}$ respectively.

Step 2: $p$-discriminant test

With $F(x,y,p)=p^2-y^2$: $F_p=2p=0\Rightarrow p=0$; substituting into $F=0$ gives $y^2=0$, i.e. $y=0$.

Step 3: Check whether $y=0$ is genuinely singular

$y=0$ satisfies the ODE, but it is already the member $C_1=0$ (or $C_2=0$) of the general solution, so it is not a singular solution.


Result

Final answer:

\[\boxed{\,y=C_1e^{x}\ \ \text{or}\ \ y=C_2e^{-x}\,}\]

No singular solution exists (same reasoning as Problem 145).

Editor's note: Problem 148 in the source material is a verbatim duplicate of Problem 145 — identical statement $(y')^2-y^2=0$ and essentially the same worked solution, almost certainly from a paste/transcription error in the original batch. This page is generated to keep the numbering intact and matches Problem 145 exactly; let us know if a different Problem 148 should replace it.