Answer:
see explanation
Step-by-step explanation:
Given
f(x) = [tex]3^{x}[/tex] , then
f(x + 1) = [tex]3^{x+1}[/tex] = [tex]3^{x}[/tex] × 3
Then
f(x) + f(x + 1)
= [tex]3^{x}[/tex] + 3. [tex]3^{x}[/tex] ← factor out [tex]3^{x}[/tex] from each term
= [tex]3^{x}[/tex] (1 + 3)
= 4. [tex]3^{x}[/tex]
= 4f(x)
