87.30.3 problem 3

Internal problem ID [23902]
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 8. Nonlinear differential equations and systems. Exercise at page 310
Problem number : 3
Date solved : Thursday, October 02, 2025 at 09:46:24 PM
CAS classification : system_of_ODEs

\begin{align*} \frac {d}{d t}x \left (t \right )&=-x \left (t \right )+y \left (t \right )\\ \frac {d}{d t}y \left (t \right )&=2 y \left (t \right ) \end{align*}

✓ Maple. Time used: 0.053 (sec). Leaf size: 27

ode:=[diff(x(t),t) = -x(t)+y(t), diff(y(t),t) = 2*y(t)]; 
dsolve(ode);
 

\begin{align*} x \left (t \right ) &= \frac {c_2 \,{\mathrm e}^{2 t}}{3}+c_1 \,{\mathrm e}^{-t} \\ y \left (t \right ) &= c_2 \,{\mathrm e}^{2 t} \\ \end{align*}

✓ Mathematica. Time used: 0.002 (sec). Leaf size: 40

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

\begin{align*} x(t)&\to \frac {1}{3} e^{-t} \left (c_2 \left (e^{3 t}-1\right )+3 c_1\right )\\ y(t)&\to c_2 e^{2 t} \end{align*}

✓ Sympy. Time used: 0.041 (sec). Leaf size: 24

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

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