x2−9x+20=0x^{2}-9 x+20=0x2−9x+20=0
x2+9x−28=0x^{2}+9 x-28=0x2+9x−28=0
x2−10x−28=0x^{2}-10 x-28=0x2−10x−28=0
x2+10x+28=0x^{2}+10 x+28=0x2+10x+28=0
