F(1) = 1 and the F (2) = 6 the f (n+1) = F(n)- F(n-1) How does the f(4) = -1

Answer 1

So we were given this info:

Let the current value of n that you are using be n = 2

Then, using the equation that you were given:

 f(n + 1) = f(n) – f(n – 1) substituting in the value of n

f(2 + 1) = f(2) – f(2 – 1) or

f(3) = f(2) – f(1)

But f(2) = 6 and f(1) = 1 so f(3) = 6 – 1 = 5

Now we have this info:

So now, let the current value of n that you are using be n = 3

Then, using the equation that you were given:

 f(n + 1) = f(n) – f(n – 1) substituting in the value of n

f(3 + 1) = f(3) – f(3 – 1) or

f(4) = f(3) – f(2)

But f(3) = 5 and f(2) = 6 so f(4) = 5 – 6 = -1

Answer 2

If f(1)=1 and f(2)=6

and f(n+1)=f(n)-f(n-1)

then f(3) or f(2+1)=f(2)-f(1)=6-1=5

so f(3)=5

then f(4) or f(3+1)= f(3)-f(2) = 5-6 =-1

so f(4)=-1