[`y=_G(x,y')`]
Book solution method
Change of Variable, new dependent variable
Mathematica ✓
cpu = 0.0399848 (sec), leaf count = 14
Maple ✓
cpu = 0.112 (sec), leaf count = 17
DSolve[x*y'[x] == (x^2 + ArcTan[y[x]])*(1 + y[x]^2),y[x],x]
Mathematica raw output
{{y[x] -> Tan[x*(x + 2*C[1])]}}
Maple raw input
dsolve(x*diff(y(x),x) = (1+y(x)^2)*(x^2+arctan(y(x))), y(x),'implicit')
Maple raw output
1/x*arctan(y(x))-x-_C1 = 0