Thread: Please help with this Question about functions

Hi I'm stuck on this question about functions.
I have attached the question. It is Q7.
I have done the first bit thats the simplify bit
but I can't do the hence show f(x)=etc. bit.

Also I'm stuck on the bit after that.
Thats the hence show a(subscript n)=2^n+5^n

Help with these two bits would be greatly appreciated.

Thanks in advance for replies.