48.5.1 problem Problem 5.1

Internal problem ID [7566]
Book : THEORY OF DIFFERENTIAL EQUATIONS IN ENGINEERING AND MECHANICS. K.T. CHAU, CRC Press. Boca Raton, FL. 2018
Section : Chapter 5. Systems of First Order Differential Equations. Section 5.11 Problems. Page 360
Problem number : Problem 5.1
Date solved : Monday, January 27, 2025 at 03:06:21 PM
CAS classification : system_of_ODEs

\begin{align*} \frac {d}{d t}x_{1} \left (t \right )&=3 x_{1} \left (t \right )-18 x_{2} \left (t \right )\\ \frac {d}{d t}x_{2} \left (t \right )&=2 x_{1} \left (t \right )-9 x_{2} \left (t \right ) \end{align*}

With initial conditions

\begin{align*} x_{1} \left (0\right ) = 2\\ x_{2} \left (0\right ) = 1 \end{align*}

✓ Solution by Maple

Time used: 0.030 (sec). Leaf size: 28

dsolve([diff(x__1(t),t) = 3*x__1(t)-18*x__2(t), diff(x__2(t),t) = 2*x__1(t)-9*x__2(t), x__1(0) = 2, x__2(0) = 1], singsol=all)
 

\begin{align*} x_{1} \left (t \right ) &= {\mathrm e}^{-3 t} \left (-6 t +2\right ) \\ x_{2} \left (t \right ) &= \frac {{\mathrm e}^{-3 t} \left (-36 t +18\right )}{18} \\ \end{align*}

✓ Solution by Mathematica

Time used: 0.004 (sec). Leaf size: 30

DSolve[{D[ x1[t],t]==3*x1[t]-18*x2[t],D[ x2[t],t]==2*x1[t]-9*x2[t]},{x1[0]==2,x2[0]==1},{x1[t],x2[t]},t,IncludeSingularSolutions -> True]
 

\begin{align*} \text {x1}(t)\to e^{-3 t} (2-6 t) \\ \text {x2}(t)\to e^{-3 t} (1-2 t) \\ \end{align*}