7.13.26 problem 27 (b)

Internal problem ID [425]
Book : Elementary Differential Equations. By C. Henry Edwards, David E. Penney and David Calvis. 6th edition. 2008
Section : Chapter 3. Power series methods. Section 3.1 (Introduction). Problems at page 206
Problem number : 27 (b)
Date solved : Wednesday, February 05, 2025 at 03:42:14 AM
CAS classification : [[_3rd_order, _missing_x]]

\begin{align*} y^{\prime \prime \prime }&=y \end{align*}

With initial conditions

\begin{align*} y \left (0\right )&=1\\ y^{\prime }\left (0\right )&=1\\ y^{\prime \prime }\left (0\right )&=-1 \end{align*}

✓ Solution by Maple

Time used: 0.033 (sec). Leaf size: 38

dsolve([diff(y(x),x$3)=y(x),y(0) = 1, D(y)(0) = 1, (D@@2)(y)(0) = -1],y(x), singsol=all)
 

\[ y = \frac {{\mathrm e}^{x}}{3}+\frac {2 \,{\mathrm e}^{-\frac {x}{2}} \sin \left (\frac {\sqrt {3}\, x}{2}\right ) \sqrt {3}}{3}+\frac {2 \,{\mathrm e}^{-\frac {x}{2}} \cos \left (\frac {\sqrt {3}\, x}{2}\right )}{3} \]

✓ Solution by Mathematica

Time used: 0.004 (sec). Leaf size: 55

DSolve[{D[y[x],{x,3}]==y[x],{y[0]==1,Derivative[1][y][0] ==1,Derivative[2][y][0] ==-1}},y[x],x,IncludeSingularSolutions -> True]
 

\[ y(x)\to \frac {1}{3} e^{-x/2} \left (e^{3 x/2}+2 \sqrt {3} \sin \left (\frac {\sqrt {3} x}{2}\right )+2 \cos \left (\frac {\sqrt {3} x}{2}\right )\right ) \]