Question

 

Решите уравнение 2*3^(x+1) - 4*3^(x-1) =42  

Answer 1

2*3^(x+1) - 4*3^(x-1) =42  
3^(x-1)=t
2*9*t-4t=42
18t-4t=42
14t=42
t=3
3^(x-1)=3^1
x-1=1
x=2