5 Решите уравнение: a) (3x - 2)² - (3x - 4)(3x + 4) = 0; б) 4y² - 81 = 0.

a) (9x² - 12x + 4) - (9x² - 16) = 0 => 9x² - 12x + 4 - 9x² + 16 = 0 => -12x + 20 = 0 => 12x = 20 => x = 20/12 = 5/3

б) 4y² - 81 = 0 => 4y² = 81 => y² = 81/4 => y = ±√(81/4) => y = ±9/2