x^2-3x=x+30-x^2
14x^2-14x-14=2x^2+x+13

x² - 3x = x + 30 - x²

x² + x² - 3x - x - 30 = 0

2x² - 4x - 30 = 0 | :2

x² - 2x - 15 = 0

D = 4 + 4 * 15 = 4 + 60 = 64

x₁ = 2 + 8 / 2 = 10 / 2 = 5

x₂ = 2 - 8 / 2 = -6 / 2 = -3

14x² - 14x - 14 = 2x² + x + 13

12x² - 15x - 27 = 0

D = 225 + 1296 = 1521

x₁ = 15 + 39 / 24 = 2.25

x₂ = 15 - 39 / 24 = -1