32.10.2 problem Exercise 35.2, page 504
Internal
problem
ID
[5996]
Book
:
Ordinary
Differential
Equations,
By
Tenenbaum
and
Pollard.
Dover,
NY
1963
Section
:
Chapter
8.
Special
second
order
equations.
Lesson
35.
Independent
variable
x
absent
Problem
number
:
Exercise
35.2,
page
504
Date
solved
:
Sunday, March 30, 2025 at 10:29:22 AM
CAS
classification
:
[[_2nd_order, _missing_x], [_2nd_order, _reducible, _mu_x_y1]]
\begin{align*} y^{3} y^{\prime \prime }&=k \end{align*}
✓ Maple. Time used: 0.221 (sec). Leaf size: 46
ode:=y(x)^3*diff(diff(y(x),x),x) = k;
dsolve(ode,y(x), singsol=all);
\begin{align*}
y &= \frac {\sqrt {c_1 \left (\left (c_2 +x \right )^{2} c_1^{2}+k \right )}}{c_1} \\
y &= -\frac {\sqrt {c_1 \left (\left (c_2 +x \right )^{2} c_1^{2}+k \right )}}{c_1} \\
\end{align*}
✓ Mathematica. Time used: 2.961 (sec). Leaf size: 63
ode=y[x]^3*D[y[x],{x,2}]==k;
ic={};
DSolve[{ode,ic},y[x],x,IncludeSingularSolutions->True]
\begin{align*}
y(x)\to -\frac {\sqrt {k+c_1{}^2 (x+c_2){}^2}}{\sqrt {c_1}} \\
y(x)\to \frac {\sqrt {k+c_1{}^2 (x+c_2){}^2}}{\sqrt {c_1}} \\
y(x)\to \text {Indeterminate} \\
\end{align*}
✓ Sympy. Time used: 0.548 (sec). Leaf size: 112
from sympy import *
x = symbols("x")
k = symbols("k")
y = Function("y")
ode = Eq(-k + y(x)**3*Derivative(y(x), (x, 2)),0)
ics = {}
dsolve(ode,func=y(x),ics=ics)
\[
\left [ \begin {cases} \frac {i \sqrt {-1 + \frac {k}{C_{1} y^{2}{\left (x \right )}}} y{\left (x \right )}}{\sqrt {C_{1}}} & \text {for}\: \left |{\frac {k}{C_{1} y^{2}{\left (x \right )}}}\right | > 1 \\\frac {\sqrt {1 - \frac {k}{C_{1} y^{2}{\left (x \right )}}} y{\left (x \right )}}{\sqrt {C_{1}}} & \text {otherwise} \end {cases} = C_{1} + x, \ \begin {cases} \frac {i \sqrt {-1 + \frac {k}{C_{1} y^{2}{\left (x \right )}}} y{\left (x \right )}}{\sqrt {C_{1}}} & \text {for}\: \left |{\frac {k}{C_{1} y^{2}{\left (x \right )}}}\right | > 1 \\\frac {\sqrt {1 - \frac {k}{C_{1} y^{2}{\left (x \right )}}} y{\left (x \right )}}{\sqrt {C_{1}}} & \text {otherwise} \end {cases} = C_{1} - x\right ]
\]