Bună!
[tex]3 {}^{x + 3} + 3 {}^{x + 2} + - 3 {}^{x} = 315 \\ (3 {}^{3} + 3 {}^{2} - 1) \times 3 {}^{x} = 315 \\ (27 + 9 - 1) \times 3 {}^{x} = 315 \\ 35 \times 3 {}^{x} = 315 \\ 3 {}^{x} = 9 \\ 3 {}^{x} = 3 {}^{2} \\ x = 2[/tex]
