_x \\ \\ OTBET: \: x \in ( - 2.25; \:2.25)" alt="16 {x}^{2} - 81 < 0 \\ (4x - 9)(4x + 9) < 0 \\ (4x - 9)(4x + 9) = 0 \\ 1) \ 4x - 9 = 0 \\ x = \frac{9}{4} = 2.25 \\ \\ 2) \: 4x + 9 = 0 \\ \\ x = - \frac{9}{4} = - 2.25 \\ \\ + + + ( - 2.25) - - - (2.25) + + + >_x \\ \\ OTBET: \: x \in ( - 2.25; \:2.25)" align="absmiddle" class="latex-formula">