Verified answer

a² - b² = (a - b)(a + b)

(4x-3)^2 - (3x+4)^2 ≤ 0

(4x - 3 - 3x - 4)(4x - 3 + 3x + 4) ≤ 0

(x - 7)(7x + 1) ≤ 0

применяем метод интервалов

++++++++[-1/7] ----------------- [7] +++++++++

x ∈ [-1/7, 7]