D = b² - 4ac | D=b^(2)-4ac

x² - 13x + 36 = 0

a = 1
b = -13
c = 36

D = b² - 4ac = (-13)² - 4 * 1 * 36 = 169 - 144 = 25

x₁ = (-b + √D) : 2a = (13+5) : 2 = 18 : 2 = 9
x₂ = (-b - √D) : 2a = (13-5) : 2 = 8 : 2 = 4

Ответ: 9; 4