15.10.14 problem 14

Internal problem ID [3101]
Book : Differential Equations by Alfred L. Nelson, Karl W. Folley, Max Coral. 3rd ed. DC heath. Boston. 1964
Section : Exercise 18, page 82
Problem number : 14
Date solved : Sunday, March 30, 2025 at 01:18:29 AM
CAS classification : [[_high_order, _missing_x]]

\begin{align*} y^{\prime \prime \prime \prime }+y^{\prime \prime }-20 y&=0 \end{align*}

✓ Maple. Time used: 0.003 (sec). Leaf size: 33

ode:=diff(diff(diff(diff(y(x),x),x),x),x)+diff(diff(y(x),x),x)-20*y(x) = 0; 
dsolve(ode,y(x), singsol=all);
 

\[ y = c_1 \,{\mathrm e}^{2 x}+c_2 \,{\mathrm e}^{-2 x}+c_3 \sin \left (\sqrt {5}\, x \right )+c_4 \cos \left (\sqrt {5}\, x \right ) \]

✓ Mathematica. Time used: 0.004 (sec). Leaf size: 44

ode=D[y[x],{x,4}]+D[y[x],{x,2}]-20*y[x]==0; 
ic={}; 
DSolve[{ode,ic},y[x],x,IncludeSingularSolutions->True]
 

\[ y(x)\to c_3 e^{-2 x}+c_4 e^{2 x}+c_1 \cos \left (\sqrt {5} x\right )+c_2 \sin \left (\sqrt {5} x\right ) \]

✓ Sympy. Time used: 0.098 (sec). Leaf size: 36

from sympy import * 
x = symbols("x") 
y = Function("y") 
ode = Eq(-20*y(x) + Derivative(y(x), (x, 2)) + Derivative(y(x), (x, 4)),0) 
ics = {} 
dsolve(ode,func=y(x),ics=ics)
 

\[ y{\left (x \right )} = C_{1} e^{- 2 x} + C_{2} e^{2 x} + C_{3} \sin {\left (\sqrt {5} x \right )} + C_{4} \cos {\left (\sqrt {5} x \right )} \]