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