\[ (a-1) b+a x^2+2 a x y(x) y'(x)+(1-a) y(x)^2+y(x)^2 y'(x)^2=0 \] ✓ Mathematica : cpu = 1.01011 (sec), leaf count = 79
\[\left \{\left \{y(x)\to -\sqrt {-2 a c_1 x+a c_1^2+b+2 c_1 x-c_1^2-x^2}\right \},\left \{y(x)\to \sqrt {-2 a c_1 x+a c_1^2+b+2 c_1 x-c_1^2-x^2}\right \}\right \}\]
✓ Maple : cpu = 0.724 (sec), leaf count = 251
\[ \left \{ y \left ( x \right ) =\sqrt {-a{x}^{2}+b},y \left ( x \right ) ={\frac {1}{a}\sqrt {-{a}^{2}{x}^{2}-2\,a\sqrt {{\it \_C1}\,{a}^{2}-{a}^{2}b-{\it \_C1}\,a+ab}x+{\it \_C1}\,a+{a}^{2}b-ab}},y \left ( x \right ) ={\frac {1}{a}\sqrt {-{a}^{2}{x}^{2}+2\,a\sqrt {{\it \_C1}\,{a}^{2}-{a}^{2}b-{\it \_C1}\,a+ab}x+{\it \_C1}\,a+{a}^{2}b-ab}},y \left ( x \right ) =-\sqrt {-a{x}^{2}+b},y \left ( x \right ) =-{\frac {1}{a}\sqrt {-{a}^{2}{x}^{2}-2\,a\sqrt {{\it \_C1}\,{a}^{2}-{a}^{2}b-{\it \_C1}\,a+ab}x+{\it \_C1}\,a+{a}^{2}b-ab}},y \left ( x \right ) =-{\frac {1}{a}\sqrt {-{a}^{2}{x}^{2}+2\,a\sqrt {{\it \_C1}\,{a}^{2}-{a}^{2}b-{\it \_C1}\,a+ab}x+{\it \_C1}\,a+{a}^{2}b-ab}} \right \} \]