83.23.18 problem 18
Internal
problem
ID
[19220]
Book
:
A
Text
book
for
differentional
equations
for
postgraduate
students
by
Ray
and
Chaturvedi.
First
edition,
1958.
BHASKAR
press.
INDIA
Section
:
Chapter
V.
Singular
solutions.
Exercise
V
at
page
76
Problem
number
:
18
Date
solved
:
Friday, March 14, 2025 at 05:04:37 AM
CAS
classification
:
[[_homogeneous, `class G`]]
\begin{align*} {y^{\prime }}^{4}&=4 y \left (x y^{\prime }-2 y\right )^{2} \end{align*}
✓ Maple. Time used: 0.099 (sec). Leaf size: 120
ode:=diff(y(x),x)^4 = 4*y(x)*(x*diff(y(x),x)-2*y(x))^2;
dsolve(ode,y(x), singsol=all);
\begin{align*}
y \left (x \right ) &= \frac {x^{4}}{16} \\
y \left (x \right ) &= 0 \\
y \left (x \right ) \left (-x +\sqrt {x^{2}-4 \sqrt {y \left (x \right )}}\right )^{-\frac {2 \sqrt {x^{2} y \left (x \right )-4 y \left (x \right )^{{3}/{2}}}}{\sqrt {x^{2}-4 \sqrt {y \left (x \right )}}\, \sqrt {y \left (x \right )}}} \left (\sqrt {x^{2}-4 \sqrt {y \left (x \right )}}+x \right )^{\frac {2 \sqrt {x^{2} y \left (x \right )-4 y \left (x \right )^{{3}/{2}}}}{\sqrt {x^{2}-4 \sqrt {y \left (x \right )}}\, \sqrt {y \left (x \right )}}}-c_{1} &= 0 \\
\end{align*}
✓ Mathematica. Time used: 4.06 (sec). Leaf size: 779
ode=D[y[x],x]^4==4*y[x]*(x*D[y[x],x]-2*y[x])^2;
ic={};
DSolve[{ode,ic},y[x],x,IncludeSingularSolutions->True]
\begin{align*}
\text {Solve}\left [\frac {\sqrt {x^2-4 \sqrt {y(x)}} \sqrt {x^2 y(x)-4 y(x)^{3/2}}}{8 y(x)-2 x^2 \sqrt {y(x)}}+\frac {\sqrt {\left (x^2-4 \sqrt {y(x)}\right ) y(x)} \log \left (\sqrt {x^2-4 \sqrt {y(x)}}-x\right )}{\sqrt {x^2-4 \sqrt {y(x)}} \sqrt {y(x)}}+\log \left (4 y(x)^{3/2}-x^2 y(x)\right )-\log \left (x^2 \left (-\sqrt {y(x)}\right )+\sqrt {x^2-4 \sqrt {y(x)}} \sqrt {x^2 y(x)-4 y(x)^{3/2}}+4 y(x)\right )&=c_1,y(x)\right ] \\
\text {Solve}\left [\frac {\sqrt {\left (x^2+4 \sqrt {y(x)}\right ) y(x)} \log \left (\sqrt {x^2+4 \sqrt {y(x)}}-x\right )}{\sqrt {x^2+4 \sqrt {y(x)}} \sqrt {y(x)}}+\frac {1}{4} \left (-\frac {2 \sqrt {x^2+4 \sqrt {y(x)}} \sqrt {y(x)}}{\sqrt {\left (x^2+4 \sqrt {y(x)}\right ) y(x)}}+4 \log \left (\sqrt {x^2+4 \sqrt {y(x)}} y(x)\right )-4 \log \left (\sqrt {\left (x^2+4 \sqrt {y(x)}\right ) y(x)}-\sqrt {x^2+4 \sqrt {y(x)}} \sqrt {y(x)}\right )\right )&=c_1,y(x)\right ] \\
\text {Solve}\left [\frac {1}{4} \left (\frac {2 \sqrt {x^2+4 \sqrt {y(x)}} \sqrt {y(x)}}{\sqrt {\left (x^2+4 \sqrt {y(x)}\right ) y(x)}}+4 \log \left (\sqrt {x^2+4 \sqrt {y(x)}} y(x)\right )-4 \log \left (\sqrt {x^2+4 \sqrt {y(x)}} \sqrt {y(x)}+\sqrt {\left (x^2+4 \sqrt {y(x)}\right ) y(x)}\right )\right )-\frac {\sqrt {\left (x^2+4 \sqrt {y(x)}\right ) y(x)} \log \left (\sqrt {x^2+4 \sqrt {y(x)}}-x\right )}{\sqrt {x^2+4 \sqrt {y(x)}} \sqrt {y(x)}}&=c_1,y(x)\right ] \\
\text {Solve}\left [\frac {1}{4} \left (\frac {2 \sqrt {x^2 y(x)-4 y(x)^{3/2}}}{\sqrt {x^2-4 \sqrt {y(x)}} \sqrt {y(x)}}+4 \log \left (4 y(x)^{3/2}-x^2 y(x)\right )-4 \log \left (x^2 \sqrt {y(x)}+\sqrt {x^2-4 \sqrt {y(x)}} \sqrt {x^2 y(x)-4 y(x)^{3/2}}-4 y(x)\right )\right )-\frac {\sqrt {\left (x^2-4 \sqrt {y(x)}\right ) y(x)} \log \left (\sqrt {x^2-4 \sqrt {y(x)}}-x\right )}{\sqrt {x^2-4 \sqrt {y(x)}} \sqrt {y(x)}}&=c_1,y(x)\right ] \\
y(x)\to 0 \\
y(x)\to \frac {x^4}{16} \\
\end{align*}
✗ Sympy
from sympy import *
x = symbols("x")
y = Function("y")
ode = Eq(-4*(x*Derivative(y(x), x) - 2*y(x))**2*y(x) + Derivative(y(x), x)**4,0)
ics = {}
dsolve(ode,func=y(x),ics=ics)
Timed Out