\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) =-1/2\,ax+1+ \left ( y \left ( x \right ) \right ) ^{2}+1/2\,a{x}^{2}y \left ( x \right ) +bxy \left ( x \right ) +1/16\,{a}^{2}{x}^{4}+1/4\,a{x}^{3}b+1/4\,{b}^{2}{x}^{2}+ \left ( y \left ( x \right ) \right ) ^{3}+3/4\,a{x}^{2} \left ( y \left ( x \right ) \right ) ^{2}+3/2\, \left ( y \left ( x \right ) \right ) ^{2}bx+3/16\,y \left ( x \right ) {a}^{2}{x}^{4}+3/4\,y \left ( x \right ) a{x}^{3}b+3/4\,y \left ( x \right ) {b}^{2}{x}^{2}+{\frac {{a}^{3}{x}^{6}}{64}}+{\frac {3\,{a}^{2}{x}^{5}b}{32}}+3/16\,a{x}^{4}{b}^{2}+1/8\,{b}^{3}{x}^{3}=0} \]
Mathematica: cpu = 0.167521 (sec), leaf count = 141 \[ \text {Solve}\left [-\frac {1}{3} (27 b+58)^{2/3} \text {RootSum}\left [\text {$\#$1}^3 (27 b+58)^{2/3}-3\ 2^{2/3} \text {$\#$1}+(27 b+58)^{2/3}\& ,\frac {\log \left (\frac {\sqrt [3]{2} \left (\frac {1}{4} \left (3 a x^2+6 b x+4\right )+3 y(x)\right )}{\sqrt [3]{27 b+58}}-\text {$\#$1}\right )}{2^{2/3}-\text {$\#$1}^2 (27 b+58)^{2/3}}\& \right ]=\frac {(27 b+58)^{2/3} x}{9\ 2^{2/3}}+c_1,y(x)\right ] \]
Maple: cpu = 0.078 (sec), leaf count = 42 \[ \left \{ y \left ( x \right ) =-{\frac {a{x}^{2}}{4}}-{\frac {bx}{2}}+{ \it RootOf} \left ( -x+2\,\int ^{{\it \_Z}}\! \left ( 2\,{{\it \_a}}^{3} +2\,{{\it \_a}}^{2}+b+2 \right ) ^{-1}{d{\it \_a}}+{\it \_C1} \right ) \right \} \]