\[ a+\left (x^2-1\right ) y'(x)-x y(x)=0 \] ✓ Mathematica : cpu = 0.0171105 (sec), leaf count = 21
\[\left \{\left \{y(x)\to a x+c_1 \sqrt {x^2-1}\right \}\right \}\] ✓ Maple : cpu = 0.017 (sec), leaf count = 20
\[ \left \{ y \left ( x \right ) =\sqrt {x-1}\sqrt {1+x}{\it \_C1}+ax \right \} \]