# Math Help - Complicated Function

1. ## Complicated Function

Hi,
please find attached the problem and the answer. I can't anderstand the first and second step of the answer. I only need a link for the topic or maybe method he used. Bdw I haven't tried to figure out the second answer but for now I only need help tackling the first one.

2. f(n+1) = 15^(n+1) - 8^(n-1)

8f(n) =
8.15^n - 8.8^(n-2) = 8.15^n - 8^(n-1)

f(n+1) - 8f(n) = 15^(n+1) - 8^(n-1) - 8.15^n + 8^(n-1)

8^(n-1)-8^(n-1)=0

-->f(n+1) - 8f(n) = 15^(n+1) - 8.15^n
= 15^n(15-8)
= 7. 15^n

Sorry... im new to this forum how do i write in maths like with the exponents??
Thank you

3. press the button to the left of the 'youtube' button and to the right of the 'php' button.

or insert tags such as

[math.][/math.] but do not include the dots

e.g.
7. 15^n $=7.15^{n}$