HELP Which represents a recursion function?

A. Xn = f(Xn)

B. Xn = f(X0)

C. Xn = f(a1)

D. Xn = f(Xn-1)

(Picture added for more info)

Choice D

This basically says "the nth term is found by computing math, aka evaluating some function, based on the (n-1)th term".

As an example, we could have a function that simply squares the input

Let's say we started at 5. It squares to 25 which in turns squares to 625, and so on. Each new term is based on the old term. Namely, we squared the old n-1 term to get the new nth term.

the 4th choice is the correct one

step-by-step explanation:

you didn't give me the choices, so i will just give you the graph so you can look at your choices and choose the right one.