76.25.15 problem 19

Internal problem ID [17749]
Book : Differential equations. An introduction to modern methods and applications. James Brannan, William E. Boyce. Third edition. Wiley 2015
Section : Chapter 6. Systems of First Order Linear Equations. Section 6.3 (Homogeneous Linear Systems with Constant Coefficients). Problems at page 408
Problem number : 19
Date solved : Thursday, March 13, 2025 at 10:48:23 AM
CAS classification : system_of_ODEs

\begin{align*} \frac {d}{d t}x_{1} \left (t \right )&=2 x_{1} \left (t \right )+2 x_{2} \left (t \right )-x_{4} \left (t \right )\\ \frac {d}{d t}x_{2} \left (t \right )&=2 x_{1} \left (t \right )-x_{2} \left (t \right )+2 x_{4} \left (t \right )\\ \frac {d}{d t}x_{3} \left (t \right )&=3 x_{3} \left (t \right )\\ \frac {d}{d t}x_{4} \left (t \right )&=-x_{1} \left (t \right )+2 x_{2} \left (t \right )+2 x_{4} \left (t \right ) \end{align*}

✓ Maple. Time used: 0.151 (sec). Leaf size: 74

ode:=[diff(x__1(t),t) = 2*x__1(t)+2*x__2(t)-x__4(t), diff(x__2(t),t) = 2*x__1(t)-x__2(t)+2*x__4(t), diff(x__3(t),t) = 3*x__3(t), diff(x__4(t),t) = -x__1(t)+2*x__2(t)+2*x__4(t)]; 
dsolve(ode);
 

\begin{align*} x_{1} \left (t \right ) &= {\mathrm e}^{-3 t} c_{2} +c_{3} {\mathrm e}^{3 t} \\ x_{2} \left (t \right ) &= -2 \,{\mathrm e}^{-3 t} c_{2} -2 c_{3} {\mathrm e}^{3 t}+c_{1} {\mathrm e}^{3 t} \\ x_{3} \left (t \right ) &= c_4 \,{\mathrm e}^{3 t} \\ x_{4} \left (t \right ) &= {\mathrm e}^{-3 t} c_{2} -5 c_{3} {\mathrm e}^{3 t}+2 c_{1} {\mathrm e}^{3 t} \\ \end{align*}

✓ Mathematica. Time used: 0.025 (sec). Leaf size: 282

ode={D[x1[t],t]==2*x1[t]+2*x2[t]-0*x3[t]-1*x4[t],D[x2[t],t]==2*x1[t]-1*x2[t]+0*x3[t]+2*x4[t],D[x3[t],t]==0*x1[t]-0*x2[t]+3*x3[t]+0*x4[t],D[x4[t],t]==-1*x1[t]+2*x2[t]+0*x3[t]+2*x4[t]}; 
ic={}; 
DSolve[{ode,ic},{x1[t],x2[t],x3[t],x4[t]},t,IncludeSingularSolutions->True]
 

\begin{align*} \text {x1}(t)\to \frac {1}{6} e^{-3 t} \left (c_1 \left (5 e^{6 t}+1\right )+(2 c_2-c_3) \left (e^{6 t}-1\right )\right ) \\ \text {x2}(t)\to \frac {1}{3} e^{-3 t} \left (c_1 \left (e^{6 t}-1\right )+c_2 \left (e^{6 t}+2\right )+c_3 \left (e^{6 t}-1\right )\right ) \\ \text {x4}(t)\to \frac {1}{6} e^{-3 t} \left (-\left (c_1 \left (e^{6 t}-1\right )\right )+2 c_2 \left (e^{6 t}-1\right )+c_3 \left (5 e^{6 t}+1\right )\right ) \\ \text {x3}(t)\to c_4 e^{3 t} \\ \text {x1}(t)\to \frac {1}{6} e^{-3 t} \left (c_1 \left (5 e^{6 t}+1\right )+(2 c_2-c_3) \left (e^{6 t}-1\right )\right ) \\ \text {x2}(t)\to \frac {1}{3} e^{-3 t} \left (c_1 \left (e^{6 t}-1\right )+c_2 \left (e^{6 t}+2\right )+c_3 \left (e^{6 t}-1\right )\right ) \\ \text {x4}(t)\to \frac {1}{6} e^{-3 t} \left (-\left (c_1 \left (e^{6 t}-1\right )\right )+2 c_2 \left (e^{6 t}-1\right )+c_3 \left (5 e^{6 t}+1\right )\right ) \\ \text {x3}(t)\to 0 \\ \end{align*}

✓ Sympy. Time used: 0.164 (sec). Leaf size: 60

from sympy import * 
t = symbols("t") 
x__1 = Function("x__1") 
x__2 = Function("x__2") 
x__3 = Function("x__3") 
x__4 = Function("x__4") 
ode=[Eq(-2*x__1(t) - 2*x__2(t) + x__4(t) + Derivative(x__1(t), t),0),Eq(-2*x__1(t) + x__2(t) - 2*x__4(t) + Derivative(x__2(t), t),0),Eq(-3*x__3(t) + Derivative(x__3(t), t),0),Eq(x__1(t) - 2*x__2(t) - 2*x__4(t) + Derivative(x__4(t), t),0)] 
ics = {} 
dsolve(ode,func=[x__1(t),x__2(t),x__3(t),x__4(t)],ics=ics)
 

\[ \left [ x^{1}{\left (t \right )} = C_{1} e^{- 3 t} - \left (C_{2} - 2 C_{3}\right ) e^{3 t}, \ x^{2}{\left (t \right )} = - 2 C_{1} e^{- 3 t} + C_{3} e^{3 t}, \ x^{3}{\left (t \right )} = C_{4} e^{3 t}, \ x^{4}{\left (t \right )} = C_{1} e^{- 3 t} + C_{2} e^{3 t}\right ] \]