X2 plus 15x equals -26

x2 + 15x = -26
x2 + 15x + 26 = -26 + 26
x2 + 15x + 26 = 0 where a = 1, b = 15, and c = 26
x = [-15 ± √(152 - 4(1)(26))]/2(1)
x = (-15 ± √121)/2
x = (-15 ± 11)/2
x = (-15 + 11)/2 = -4/2 = -2 or x = (-15 - 11)/2 = -26/2 = -13