7x2−8x−12=07 x^{2}-8 x-12=07x2−8x−12=0
7x2−20x=07 x^{2}-20 x=07x2−20x=0
7x2+8x−12=07 x^{2}+8 x-12=07x2+8x−12=0
7x2+8x=07 x^{2}+8 x=07x2+8x=0
