\[ \lambda y(x)+y^{(4)}(x)=0 \] ✓ Mathematica : cpu = 0.0041609 (sec), leaf count = 76
DSolve[lambda*y[x] + Derivative[4][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to c_1 e^{(-1)^{3/4} \sqrt [4]{\lambda } x}+c_2 e^{-\sqrt [4]{-1} \sqrt [4]{\lambda } x}+c_3 e^{-(-1)^{3/4} \sqrt [4]{\lambda } x}+c_4 e^{\sqrt [4]{-1} \sqrt [4]{\lambda } x}\right \}\right \}\] ✓ Maple : cpu = 0.02 (sec), leaf count = 50
dsolve(diff(diff(diff(diff(y(x),x),x),x),x)+lambda*y(x)=0,y(x))
\[y \left (x \right ) = c_{1} {\mathrm e}^{-i \left (-\lambda \right )^{\frac {1}{4}} x}+c_{2} {\mathrm e}^{i \left (-\lambda \right )^{\frac {1}{4}} x}+c_{3} {\mathrm e}^{-\left (-\lambda \right )^{\frac {1}{4}} x}+c_{4} {\mathrm e}^{\left (-\lambda \right )^{\frac {1}{4}} x}\]