87.20.18 problem 19

Internal problem ID [23703]
Book : Ordinary differential equations with modern applications. Ladas, G. E. and Finizio, N. Wadsworth Publishing. California. 1978. ISBN 0-534-00552-7. QA372.F56
Section : Chapter 3. Linear Systems. Exercise at page 161
Problem number : 19
Date solved : Thursday, October 02, 2025 at 09:44:25 PM
CAS classification : system_of_ODEs

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

✓ Maple. Time used: 0.042 (sec). Leaf size: 19

ode:=[diff(x(t),t) = -x(t), diff(y(t),t) = -y(t)]; 
dsolve(ode);
 

\begin{align*} x \left (t \right ) &= c_2 \,{\mathrm e}^{-t} \\ y \left (t \right ) &= c_1 \,{\mathrm e}^{-t} \\ \end{align*}

✓ Mathematica. Time used: 0.022 (sec). Leaf size: 65

ode={D[x[t],t]==-x[t],D[y[t],t]==-y[t]}; 
ic={}; 
DSolve[{ode,ic},{x[t],y[t]},t,IncludeSingularSolutions->True]
 

\begin{align*} x(t)&\to c_1 e^{-t}\\ y(t)&\to c_2 e^{-t}\\ x(t)&\to c_1 e^{-t}\\ y(t)&\to 0\\ x(t)&\to 0\\ y(t)&\to c_2 e^{-t}\\ x(t)&\to 0\\ y(t)&\to 0 \end{align*}

✓ Sympy. Time used: 0.037 (sec). Leaf size: 14

from sympy import * 
t = symbols("t") 
x = Function("x") 
y = Function("y") 
ode=[Eq(x(t) + Derivative(x(t), t),0),Eq(y(t) + Derivative(y(t), t),0)] 
ics = {} 
dsolve(ode,func=[x(t),y(t)],ics=ics)
 

\[ \left [ x{\left (t \right )} = C_{1} e^{- t}, \ y{\left (t \right )} = C_{2} e^{- t}\right ] \]