ODE
\[ y''''(x)+4 e^{-x} \cos (x)=0 \] ODE Classification
[[_high_order, _quadrature]]
Book solution method
TO DO
Mathematica ✓
cpu = 0.0504503 (sec), leaf count = 30
\[\left \{\left \{y(x)\to x \left (x \left (c_4 x+c_3\right )+c_2\right )+c_1+e^{-x} \cos (x)\right \}\right \}\]
Maple ✓
cpu = 0.023 (sec), leaf count = 28
\[ \left \{ y \left ( x \right ) ={{\rm e}^{-x}}\cos \left ( x \right ) +{\frac {{x}^{3}{\it \_C1}}{6}}+{\frac {{x}^{2}{\it \_C2}}{2}}+{\it \_C3}\,x+{\it \_C4} \right \} \] Mathematica raw input
DSolve[(4*Cos[x])/E^x + y''''[x] == 0,y[x],x]
Mathematica raw output
{{y[x] -> C[1] + x*(C[2] + x*(C[3] + x*C[4])) + Cos[x]/E^x}}
Maple raw input
dsolve(diff(diff(diff(diff(y(x),x),x),x),x)+4*exp(-x)*cos(x) = 0, y(x),'implicit')
Maple raw output
y(x) = exp(-x)*cos(x)+1/6*x^3*_C1+1/2*x^2*_C2+_C3*x+_C4