Question

A sequence is defined recursively using the formula f(n + 1) = f(n) – 5 . Which sequence could be generated using this formula?

1, –5, 25, –125, ...
2, 10, 50, 250, ...
3, –2, –7, –12, ...
4, 9, 14, 19, ...

Answer 1

@A_clan do you know how to do these?

Answer 2

When you substitute n=1,2,3,.. in the formula, we get
f(2) = f(1) -5
f(3)=f(2) -5
f(4)=f(3) -5 and so on
which shows that any term in the sequence is 5 less than its predecessor.
So for the answer, you need to look for a sequence which is decreasing by 5.