x2+4x+13=0x^{2}+4 x+13=0x2+4x+13=0
x2−4x+13=0x^{2}-4 x+13=0x2−4x+13=0
x2+4x−13=0x^{2}+4 x-13=0x2+4x−13=0
x2−4x−13=0x^{2}-4 x-13=0x2−4x−13=0