\[ y^{(4)}(x)=0 \] ✓ Mathematica : cpu = 0.0032823 (sec), leaf count = 24
DSolve[Derivative[4][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to c_4 x^3+c_3 x^2+c_2 x+c_1\right \}\right \}\] ✓ Maple : cpu = 0.013 (sec), leaf count = 21
dsolve(diff(diff(diff(diff(y(x),x),x),x),x)=0,y(x))
\[y \left (x \right ) = \frac {1}{6} x^{3} c_{1}+\frac {1}{2} x^{2} c_{2}+c_{3} x +c_{4}\]