\[ y'(x)^4-(y(x)-a)^3 (y(x)-b)^2=0 \] ✓ Mathematica : cpu = 0.872664 (sec), leaf count = 383
\[\left \{\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [4]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{4},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [4]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1-\sqrt [4]{-1} x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [4]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{4},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [4]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1+\sqrt [4]{-1} x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [4]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{4},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [4]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1-(-1)^{3/4} x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [4]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{4},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [4]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1+(-1)^{3/4} x\right ]\right \}\right \}\] ✓ Maple : cpu = 0.178 (sec), leaf count = 144
\[ \left \{ x-\int ^{y \left ( x \right ) }\!{\frac {1}{\sqrt [4]{ \left ( {\it \_a}-a \right ) ^{3} \left ( {\it \_a}-b \right ) ^{2}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!{-i{\frac {1}{\sqrt [4]{- \left ( -{\it \_a}+a \right ) ^{3} \left ( -{\it \_a}+b \right ) ^{2}}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!{i{\frac {1}{\sqrt [4]{- \left ( -{\it \_a}+a \right ) ^{3} \left ( -{\it \_a}+b \right ) ^{2}}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!-{\frac {1}{\sqrt [4]{- \left ( -{\it \_a}+a \right ) ^{3} \left ( -{\it \_a}+b \right ) ^{2}}}}{d{\it \_a}}-{\it \_C1}=0,y \left ( x \right ) =a,y \left ( x \right ) =b \right \} \]