[[_1st_order, `_with_symmetry_[F(x),G(y)]`]]
Book solution method
No Missing Variables ODE, Solve for
Mathematica ✓
cpu = 0.416386 (sec), leaf count = 26
Maple ✓
cpu = 0.449 (sec), leaf count = 36
DSolve[x^2 + 2*x*y[x]*y'[x] + (a^2 - x^2)*y'[x]^2 == 0,y[x],x]
Mathematica raw output
{{y[x] -> (a^2 - x^2 + C[1]^2)/(2*C[1])}}
Maple raw input
dsolve((a^2-x^2)*diff(y(x),x)^2+2*x*y(x)*diff(y(x),x)+x^2 = 0, y(x),'implicit')
Maple raw output
y(x)^2-a^2+x^2 = 0, y(x) = _C1*x^2-_C1*a^2-1/4/_C1