(x в квадрате-6x)+14(x-3)в квадрате=81

(x^2-6x)+14(x-3)^2=81,

x^2-6x+14x^2-84x+126=81,

15x^2-90x+45=0,

x^2-6x+3=0,

D=24,

x1=3-√6,

x2=3+√6.

x² - 6x + 14(x-3)² = 81

x² - 6x + 14(x²- 6x + 9) = 81

x² - 6x + 14x² - 84x + 126 = 81

15x² - 90x + 45 = 0

x² - 6x + 3 = 0

D = 6² - 12 = 24

√D = 2√6

x₁ = (6 + 2√6):2 = 3 + √6

x₂ = (6 - 2√6):2 = 3 - √6