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