80.5.6 problem B 4

Internal problem ID [21227]
Book : A Textbook on Ordinary Differential Equations by Shair Ahmad and Antonio Ambrosetti. Second edition. ISBN 978-3-319-16407-6. Springer 2015
Section : Chapter 5. Second order equations. Excercise 5.9 at page 119
Problem number : B 4
Date solved : Thursday, October 02, 2025 at 07:27:05 PM
CAS classification : [[_2nd_order, _missing_x]]

\begin{align*} x^{\prime \prime }+2 x^{\prime }-15 x&=0 \end{align*}

With initial conditions

\begin{align*} x \left (0\right )&=1 \\ x^{\prime }\left (0\right )&=1 \\ \end{align*}

✓ Maple. Time used: 0.016 (sec). Leaf size: 17

ode:=diff(diff(x(t),t),t)+2*diff(x(t),t)-15*x(t) = 0; 
ic:=[x(0) = 1, D(x)(0) = 1]; 
dsolve([ode,op(ic)],x(t), singsol=all);
 

\[ x = \frac {{\mathrm e}^{-5 t}}{4}+\frac {3 \,{\mathrm e}^{3 t}}{4} \]

✓ Mathematica. Time used: 0.011 (sec). Leaf size: 23

ode=D[x[t],{t,2}]+2*D[x[t],t]-15*x[t]==0; 
ic={x[0]==1,Derivative[1][x][0] ==1}; 
DSolve[{ode,ic},x[t],t,IncludeSingularSolutions->True]
 

\begin{align*} x(t)&\to \frac {1}{4} e^{-5 t} \left (3 e^{8 t}+1\right ) \end{align*}

✓ Sympy. Time used: 0.103 (sec). Leaf size: 19

from sympy import * 
t = symbols("t") 
x = Function("x") 
ode = Eq(-15*x(t) + 2*Derivative(x(t), t) + Derivative(x(t), (t, 2)),0) 
ics = {x(0): 1, Subs(Derivative(x(t), t), t, 0): 1} 
dsolve(ode,func=x(t),ics=ics)
 

\[ x{\left (t \right )} = \frac {3 e^{3 t}}{4} + \frac {e^{- 5 t}}{4} \]