log₂(x² - 1) = 3log₂((x + 1)/(x - 1))
log₂(x² - 1) = log₂((x + 1)/(x - 1))³
x² - 1 = ((x + 1)/(x - 1))³
(x + 1)(x - 1) = (x + 1)³/(x - 1)³
(x + 1)(x - 1)⁴ - (x + 1)³ = 0
(x + 1)((x - 1)⁴ - (x + 1)²) = 0
x + 1 = 0 или (x - 1)⁴ - (x + 1)² = 0
х₁ = -1 ((x - 1)² - (x + 1))·((x - 1)²+ (x + 1)) = 0
(x² - 2х + 1 - x - 1)·(x² - 2х + 1 + x + 1) = 0
(x² - 3х)·(x² - х + 2) = 0
х(x - 3)·(x² - х + 2) = 0
х₂ = 0; х₃ = 3.
х₁ = -1 и х₂ = 0 - не удовлетвряют данное уравнение
Ответ: 3.