66.16.9 problem 9

Internal problem ID [16192]
Book : DIFFERENTIAL EQUATIONS by Paul Blanchard, Robert L. Devaney, Glen R. Hall. 4th edition. Brooks/Cole. Boston, USA. 2012
Section : Chapter 4. Forcing and Resonance. Section 4.1 page 399
Problem number : 9
Date solved : Thursday, October 02, 2025 at 10:43:25 AM
CAS classification : [[_2nd_order, _with_linear_symmetries]]

\begin{align*} y^{\prime \prime }+6 y^{\prime }+8 y&={\mathrm e}^{-t} \end{align*}

With initial conditions

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

✓ Maple. Time used: 0.024 (sec). Leaf size: 22

ode:=diff(diff(y(t),t),t)+6*diff(y(t),t)+8*y(t) = exp(-t); 
ic:=[y(0) = 0, D(y)(0) = 0]; 
dsolve([ode,op(ic)],y(t), singsol=all);
 

\[ y = \frac {\left (2 \,{\mathrm e}^{t}+1\right ) \left ({\mathrm e}^{t}-1\right )^{2} {\mathrm e}^{-4 t}}{6} \]

✓ Mathematica. Time used: 0.022 (sec). Leaf size: 28

ode=D[y[t],{t,2}]+6*D[y[t],t]+8*y[t]==Exp[-t]; 
ic={y[0]==0,Derivative[1][y][0] ==0}; 
DSolve[{ode,ic},y[t],t,IncludeSingularSolutions->True]
 

\begin{align*} y(t)&\to \frac {1}{6} e^{-4 t} \left (e^t-1\right )^2 \left (2 e^t+1\right ) \end{align*}

✓ Sympy. Time used: 0.169 (sec). Leaf size: 24

from sympy import * 
t = symbols("t") 
y = Function("y") 
ode = Eq(8*y(t) + 6*Derivative(y(t), t) + Derivative(y(t), (t, 2)) - exp(-t),0) 
ics = {y(0): 0, Subs(Derivative(y(t), t), t, 0): 0} 
dsolve(ode,func=y(t),ics=ics)
 

\[ y{\left (t \right )} = \left (\frac {1}{3} - \frac {e^{- t}}{2} + \frac {e^{- 3 t}}{6}\right ) e^{- t} \]