[tex] log_{a}(ac ^{3} ) = log_{a}(a) + log_{a}( {c}^{3} ) = \\ = 1 + 3 log_{a}(c) = 1 + 3 \times 5 = 16[/tex]

ответ: 16

[tex]2 \times {9}^{x} - 3 \times {3}^{x} - 9 = 0 \\ 2 \times {( {3}^{x}) }^{2} - 3 \times {3}^{x} - 9 = 0 \\ {3}^{x} = y > 0 \\ 2 {y}^{2} - 3y - 9 = 0[/tex]

[tex]y_{1,2}= \frac{ 3 ± \sqrt{ {( - 3) - 4 \times 2 \times ( - 9)}^{2} } }{2 \times 2} = \frac{3 ± 9}{4} \\ y_{1} = 3 \\ y_{1} = - 1.5 < 0[/tex]

y2 <0 не подходит, т.к

[tex]y = {3}^{x} > 0[/tex]

возвращаемся к нашей замене

[tex] {3}^{x} = 3 \\ x = 1[/tex]

ответ: х=1