72.10.10 problem 10

Internal problem ID [14742]
Book : DIFFERENTIAL EQUATIONS by Paul Blanchard, Robert L. Devaney, Glen R. Hall. 4th edition. Brooks/Cole. Boston, USA. 2012
Section : Chapter 3. Linear Systems. Exercises section 3.2. page 277
Problem number : 10
Date solved : Thursday, March 13, 2025 at 04:18:04 AM
CAS classification : system_of_ODEs

\begin{align*} \frac {d}{d t}x \left (t \right )&=-x \left (t \right )-2 y \left (t \right )\\ \frac {d}{d t}y \left (t \right )&=x \left (t \right )-4 y \left (t \right ) \end{align*}

✓ Maple. Time used: 0.041 (sec). Leaf size: 34

ode:=[diff(x(t),t) = -x(t)-2*y(t), diff(y(t),t) = x(t)-4*y(t)]; 
dsolve(ode);
 

\begin{align*} x \left (t \right ) &= {\mathrm e}^{-3 t} c_{1} +{\mathrm e}^{-2 t} c_{2} \\ y &= {\mathrm e}^{-3 t} c_{1} +\frac {{\mathrm e}^{-2 t} c_{2}}{2} \\ \end{align*}

✓ Mathematica. Time used: 0.003 (sec). Leaf size: 58

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

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

✓ Sympy. Time used: 0.083 (sec). Leaf size: 32

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

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