Question

$3^{x+1} + 3^{x-1} textless 28$

Answer 1

3^(x+1)+3^(x-1)<28
9*3^(x-1)+3^(x-1)<28
(9+1)*3^(x-1)<28
3^(x-1)<28/10
3^(x-1)<14/5
x-1 < log(3, 14/5)
x < 1 + log(3, 14/5)
x < log(3, 42/5)