Нужно развязать уравнение

a) x^2 - x - 12 = 0

D = b^2 - 4ac = 1 + 48 = 49 = 7^2

x1,2 = (-b +- √D) / 2a = (1 +- 7) / 2

x1 = (1 + 7) / 2 = 4             x2 = (1 - 7) / 2 = -3

б) 3z^2 - 5z - 2 = 0

D = b^2 - 4ac = 25 + 24 = 49 = 7^2

x1,2 = (-b +- √D) / 2a = (5 +- 7) / 6

x1 = (5 + 7) / 6 = 2              x2 = (5 - 7) / 6 = -1/3

в) (x + 2)^2 - x(x - 3) = 23

x^2 + 4x + 4 - x^2 + 3x = 23

7x = 19

x = 19/7