✓ Mathematica : cpu = 0.0821509 (sec), leaf count = 49
DSolve[(1 - a^2)*x^2 + 2*x*y[x]*Derivative[1][y][x] + (-(a^2*x^2) + y[x]^2)*Derivative[1][y][x]^2 == 0,y[x],x]
✓ Maple : cpu = 0.203 (sec), leaf count = 159
dsolve((y(x)^2-a^2*x^2)*diff(y(x),x)^2+2*x*y(x)*diff(y(x),x)+(-a^2+1)*x^2 = 0,y(x))