\[ a y(x)^2-5 y'(x)^2+4 y(x) y''(x)=0 \] ✓ Mathematica : cpu = 0.15646 (sec), leaf count = 26
\[\left \{\left \{y(x)\to c_2 \text {sech}^4\left (\frac {1}{4} \sqrt {a} (x-4 c_1)\right )\right \}\right \}\] ✓ Maple : cpu = 0.486 (sec), leaf count = 33
\[ \left \{ y \left ( x \right ) =16\,{\frac { \left ( {{\rm e}^{1/4\,\sqrt {a}x}} \right ) ^{4}{a}^{2}}{ \left ( {{\rm e}^{1/2\,\sqrt {a}x}}{\it \_C1}-{\it \_C2} \right ) ^{4}}} \right \} \]