\[ 8 y''(x)+9 y'(x)^4=0 \] ✓ Mathematica : cpu = 0.0775424 (sec), leaf count = 92
DSolve[9*Derivative[1][y][x]^4 + 8*Derivative[2][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to c_2-\frac {1}{3} \sqrt [3]{-\frac {1}{3}} (9 x-8 c_1){}^{2/3}\right \},\left \{y(x)\to \frac {(9 x-8 c_1){}^{2/3}}{3 \sqrt [3]{3}}+c_2\right \},\left \{y(x)\to \frac {(-1)^{2/3} (9 x-8 c_1){}^{2/3}}{3 \sqrt [3]{3}}+c_2\right \}\right \}\] ✓ Maple : cpu = 0.979 (sec), leaf count = 51
dsolve(8*diff(diff(y(x),x),x)+9*diff(y(x),x)^4=0,y(x))
\[y \left (x \right ) = \left (x +c_{1}\right )^{\frac {2}{3}}+c_{2}\]