Answer:
Step-by-step explanation:
hello :
f(n)=f(n-1)+2
means : f(n)-f(n-1)=2
this is the arithmetic seq when the common dif is d= 2 and the first term is : 9
the n-ieme term is : f(n) = f(1) +(n-1)d
f(n) =9+2(n-1)
f(n) = 2n+7
so : f(5) = 2(5)+7 = 17
