Internal problem ID [9415]
Internal file name [OUTPUT/8355_Monday_June_06_2022_02_49_35_AM_73404355/index.tex]
Book: Differential Gleichungen, E. Kamke, 3rd ed. Chelsea Pub. NY, 1948
Section: Chapter 2, linear second order
Problem number: 1086.
ODE order: 2.
ODE degree: 1.
The type(s) of ODE detected by this program : "second_order_airy", "second_order_bessel_ode"
Maple gives the following as the ode type
[[_Emden, _Fowler]]
\[ \boxed {4 y^{\prime \prime }+9 y x=0} \]
This is Airy ODE. It has the general form \[ a y^{\prime \prime } + b y^{\prime } + c y x = F(x) \] Where in this case \begin {align*} a &= 4\\ b &= 0\\ c &= 9\\ F &= 0 \end {align*}
Therefore the solution to the homogeneous Airy ODE becomes \[ y = {\mathrm e}^{-\frac {b x}{2 a}} \left (c_{1} \operatorname {AiryAi}\left (-\frac {\left (\frac {c}{a}\right )^{\frac {1}{3}} \left (c x a -\frac {b^{2}}{4}\right )}{c a}\right )+c_{2} \operatorname {AiryBi}\left (-\frac {\left (\frac {c}{a}\right )^{\frac {1}{3}} \left (c x a -\frac {b^{2}}{4}\right )}{c a}\right )\right ) \] Substituting the values for \(a,b,c\) gives \[ y = c_{1} \operatorname {AiryAi}\left (-\frac {9^{\frac {1}{3}} 4^{\frac {2}{3}} x}{4}\right )+c_{2} \operatorname {AiryBi}\left (-\frac {9^{\frac {1}{3}} 4^{\frac {2}{3}} x}{4}\right ) \]
The solution(s) found are the following \begin{align*} \tag{1} y &= c_{1} \operatorname {AiryAi}\left (-\frac {9^{\frac {1}{3}} 4^{\frac {2}{3}} x}{4}\right )+c_{2} \operatorname {AiryBi}\left (-\frac {9^{\frac {1}{3}} 4^{\frac {2}{3}} x}{4}\right ) \\ \end{align*}
Verification of solutions
\[ y = c_{1} \operatorname {AiryAi}\left (-\frac {9^{\frac {1}{3}} 4^{\frac {2}{3}} x}{4}\right )+c_{2} \operatorname {AiryBi}\left (-\frac {9^{\frac {1}{3}} 4^{\frac {2}{3}} x}{4}\right ) \] Verified OK.
Writing the ode as \begin {align*} x^{2} y^{\prime \prime }+\frac {9 x^{3} y}{4} = 0\tag {1} \end {align*}
Bessel ode has the form \begin {align*} x^{2} y^{\prime \prime }+y^{\prime } x +\left (-n^{2}+x^{2}\right ) y = 0\tag {2} \end {align*}
The generalized form of Bessel ode is given by Bowman (1958) as the following \begin {align*} x^{2} y^{\prime \prime }+\left (1-2 \alpha \right ) x y^{\prime }+\left (\beta ^{2} \gamma ^{2} x^{2 \gamma }-n^{2} \gamma ^{2}+\alpha ^{2}\right ) y = 0\tag {3} \end {align*}
With the standard solution \begin {align*} y&=x^{\alpha } \left (c_{1} \operatorname {BesselJ}\left (n , \beta \,x^{\gamma }\right )+c_{2} \operatorname {BesselY}\left (n , \beta \,x^{\gamma }\right )\right )\tag {4} \end {align*}
Comparing (3) to (1) and solving for \(\alpha ,\beta ,n,\gamma \) gives \begin {align*} \alpha &= {\frac {1}{2}}\\ \beta &= 1\\ n &= {\frac {1}{3}}\\ \gamma &= {\frac {3}{2}} \end {align*}
Substituting all the above into (4) gives the solution as \begin {align*} y = c_{1} \sqrt {x}\, \operatorname {BesselJ}\left (\frac {1}{3}, x^{\frac {3}{2}}\right )+c_{2} \sqrt {x}\, \operatorname {BesselY}\left (\frac {1}{3}, x^{\frac {3}{2}}\right ) \end {align*}
Summary
The solution(s) found are the following \begin{align*} \tag{1} y &= c_{1} \sqrt {x}\, \operatorname {BesselJ}\left (\frac {1}{3}, x^{\frac {3}{2}}\right )+c_{2} \sqrt {x}\, \operatorname {BesselY}\left (\frac {1}{3}, x^{\frac {3}{2}}\right ) \\ \end{align*}
Verification of solutions
\[ y = c_{1} \sqrt {x}\, \operatorname {BesselJ}\left (\frac {1}{3}, x^{\frac {3}{2}}\right )+c_{2} \sqrt {x}\, \operatorname {BesselY}\left (\frac {1}{3}, x^{\frac {3}{2}}\right ) \] Verified OK.
\[ \begin {array}{lll} & {} & \textrm {Let's solve}\hspace {3pt} \\ {} & {} & 4 \frac {d}{d x}y^{\prime }+9 y x =0 \\ \bullet & {} & \textrm {Highest derivative means the order of the ODE is}\hspace {3pt} 2 \\ {} & {} & \frac {d}{d x}y^{\prime } \\ \bullet & {} & \textrm {Isolate 2nd derivative}\hspace {3pt} \\ {} & {} & \frac {d}{d x}y^{\prime }=-\frac {9 y x}{4} \\ \bullet & {} & \textrm {Group terms with}\hspace {3pt} y\hspace {3pt}\textrm {on the lhs of the ODE and the rest on the rhs of the ODE; ODE is linear}\hspace {3pt} \\ {} & {} & \frac {d}{d x}y^{\prime }+\frac {9 y x}{4}=0 \\ \bullet & {} & \textrm {Multiply by denominators}\hspace {3pt} \\ {} & {} & 4 \frac {d}{d x}y^{\prime }+9 y x =0 \\ \bullet & {} & \textrm {Assume series solution for}\hspace {3pt} y \\ {} & {} & y=\moverset {\infty }{\munderset {k =0}{\sum }}a_{k} x^{k} \\ \square & {} & \textrm {Rewrite ODE with series expansions}\hspace {3pt} \\ {} & \circ & \textrm {Convert}\hspace {3pt} x \cdot y\hspace {3pt}\textrm {to series expansion}\hspace {3pt} \\ {} & {} & x \cdot y=\moverset {\infty }{\munderset {k =0}{\sum }}a_{k} x^{k +1} \\ {} & \circ & \textrm {Shift index using}\hspace {3pt} k \mathrm {->}k -1 \\ {} & {} & x \cdot y=\moverset {\infty }{\munderset {k =1}{\sum }}a_{k -1} x^{k} \\ {} & \circ & \textrm {Convert}\hspace {3pt} \frac {d}{d x}y^{\prime }\hspace {3pt}\textrm {to series expansion}\hspace {3pt} \\ {} & {} & \frac {d}{d x}y^{\prime }=\moverset {\infty }{\munderset {k =2}{\sum }}a_{k} k \left (k -1\right ) x^{k -2} \\ {} & \circ & \textrm {Shift index using}\hspace {3pt} k \mathrm {->}k +2 \\ {} & {} & \frac {d}{d x}y^{\prime }=\moverset {\infty }{\munderset {k =0}{\sum }}a_{k +2} \left (k +2\right ) \left (k +1\right ) x^{k} \\ & {} & \textrm {Rewrite ODE with series expansions}\hspace {3pt} \\ {} & {} & 8 a_{2}+\left (\moverset {\infty }{\munderset {k =1}{\sum }}\left (4 a_{k +2} \left (k +2\right ) \left (k +1\right )+9 a_{k -1}\right ) x^{k}\right )=0 \\ \bullet & {} & \textrm {Each term must be 0}\hspace {3pt} \\ {} & {} & 8 a_{2}=0 \\ \bullet & {} & \textrm {Each term in the series must be 0, giving the recursion relation}\hspace {3pt} \\ {} & {} & 4 \left (k^{2}+3 k +2\right ) a_{k +2}+9 a_{k -1}=0 \\ \bullet & {} & \textrm {Shift index using}\hspace {3pt} k \mathrm {->}k +1 \\ {} & {} & 4 \left (\left (k +1\right )^{2}+3 k +5\right ) a_{k +3}+9 a_{k}=0 \\ \bullet & {} & \textrm {Recursion relation that defines the series solution to the ODE}\hspace {3pt} \\ {} & {} & \left [y=\moverset {\infty }{\munderset {k =0}{\sum }}a_{k} x^{k}, a_{k +3}=-\frac {9 a_{k}}{4 \left (k^{2}+5 k +6\right )}, 8 a_{2}=0\right ] \end {array} \]
Maple trace
`Methods for second order ODEs: --- Trying classification methods --- trying a quadrature checking if the LODE has constant coefficients checking if the LODE is of Euler type trying a symmetry of the form [xi=0, eta=F(x)] checking if the LODE is missing y -> Trying a Liouvillian solution using Kovacics algorithm <- No Liouvillian solutions exists -> Trying a solution in terms of special functions: -> Bessel <- Bessel successful <- special function solution successful`
✓ Solution by Maple
Time used: 0.0 (sec). Leaf size: 29
dsolve(4*diff(diff(y(x),x),x)+9*x*y(x)=0,y(x), singsol=all)
\[ y \left (x \right ) = c_{1} \operatorname {AiryAi}\left (-\frac {3^{\frac {2}{3}} 2^{\frac {1}{3}} x}{2}\right )+c_{2} \operatorname {AiryBi}\left (-\frac {3^{\frac {2}{3}} 2^{\frac {1}{3}} x}{2}\right ) \]
✓ Solution by Mathematica
Time used: 0.024 (sec). Leaf size: 42
DSolve[9*x*y[x] + 4*y''[x] == 0,y[x],x,IncludeSingularSolutions -> True]
\[ y(x)\to c_1 \operatorname {AiryAi}\left (\sqrt [3]{-1} \left (\frac {3}{2}\right )^{2/3} x\right )+c_2 \operatorname {AiryBi}\left (\sqrt [3]{-1} \left (\frac {3}{2}\right )^{2/3} x\right ) \]