Hey there! Here's your answer:
f (n + 1) = f(n) - 5
Here's why:
6, 1, –4, –9, –14, ...
We need to analyze our current sequence to know what pattern will follow.
6 - 5 = 1
1 - 5 = -4
-4 - 5 = -9
-9 - 5 = -14
(And So On)
We can see successive terms are found by subtracting 5 from previous terms.
I hope this helps! Have a good day :).