70.9.11 problem 11

Internal problem ID [18808]
Book : Differential equations. An introduction to modern methods and applications. James Brannan, William E. Boyce. Third edition. Wiley 2015
Section : Chapter 3. Systems of two first order equations. Section 3.5 (Repeated Eigenvalues). Problems at page 188
Problem number : 11
Date solved : Thursday, October 02, 2025 at 03:31:04 PM
CAS classification : system_of_ODEs

\begin{align*} \frac {d}{d t}x \left (t \right )&=-3 x \left (t \right )+\frac {5 y \left (t \right )}{2}\\ \frac {d}{d t}y \left (t \right )&=-\frac {5 x \left (t \right )}{2}+2 y \left (t \right ) \end{align*}

With initial conditions

\begin{align*} x \left (0\right )&=3 \\ y \left (0\right )&=1 \\ \end{align*}

✓ Maple. Time used: 0.140 (sec). Leaf size: 28

ode:=[diff(x(t),t) = -3*x(t)+5/2*y(t), diff(y(t),t) = -5/2*x(t)+2*y(t)]; 
ic:=[x(0) = 3, y(0) = 1]; 
dsolve([ode,op(ic)]);
 

\begin{align*} x \left (t \right ) &= {\mathrm e}^{-\frac {t}{2}} \left (-5 t +3\right ) \\ y \left (t \right ) &= \frac {{\mathrm e}^{-\frac {t}{2}} \left (-25 t +5\right )}{5} \\ \end{align*}

✓ Mathematica. Time used: 0.002 (sec). Leaf size: 34

ode={D[x[t],t]==-3*x[t]+5/2*y[t],D[y[t],t]==-5/2*x[t]+2*y[t]}; 
ic={x[0]==3,y[0]==1}; 
DSolve[{ode,ic},{x[t],y[t]},t,IncludeSingularSolutions->True]
 

\begin{align*} x(t)&\to e^{-t/2} (3-5 t)\\ y(t)&\to e^{-t/2} (1-5 t) \end{align*}

✓ Sympy. Time used: 0.066 (sec). Leaf size: 53

from sympy import * 
t = symbols("t") 
x = Function("x") 
y = Function("y") 
ode=[Eq(3*x(t) - 5*y(t)/2 + Derivative(x(t), t),0),Eq(5*x(t)/2 - 2*y(t) + Derivative(y(t), t),0)] 
ics = {} 
dsolve(ode,func=[x(t),y(t)],ics=ics)
 

\[ \left [ x{\left (t \right )} = - \frac {5 C_{2} t e^{- \frac {t}{2}}}{2} - \left (\frac {5 C_{1}}{2} - C_{2}\right ) e^{- \frac {t}{2}}, \ y{\left (t \right )} = - \frac {5 C_{1} e^{- \frac {t}{2}}}{2} - \frac {5 C_{2} t e^{- \frac {t}{2}}}{2}\right ] \]