Question

21 решите пожалуйста

Answer 1

$x^2(-x^2-81) leq 81(-x^2-81) \\ x^2(-x^2-81) -81(-x^2-81) leq 0 \\ (-x^2-81)(x^2-81) leq 0 \\-(x^2+81)(x^2-81) leq 0 \\ (x^2+81)(x^2-81) geq 0 \\ left { {{x geq 9} atop {x leq -9}} right. \\ x in (-infty; -9] cup [9;+infty)$