def roots(a, b, c):
"""
Return roots of a*x^2+b*x+c.
"""
s = (b*b - 4*a*c).sqrt()
return (-b + s)/(2*a)
B = CDF(25)
%time v = [roots(a,b,c) for a in [-B..B] for b in [-B..B] for c in [-B..B] if a]
%time show(points(v, pointsize=1, color='black'), svg=False, figsize=[12,12], xmin=-sqrt(B), xmax=sqrt(B))
CPU time: 1.66 s, Wall time: 1.66 s
CPU time: 7.99 s, Wall time: 10.84 s