Question

I think it is d, can someone tell me if I'm right?

Chenoa starts with $250 in her savings account. Each month she adds $15.

Which recursive function rule models the total amount in Chenoa’s savings account at the end of each month?

a. a n =15⋅ a n−1 ​ and a 1 =250
b. a n =15+ a n−1 ​ and a 1 =250
c. a n =250+ a n−1 and a 1 =15
d. a n =250⋅ a n−1 and a 1 =15

Answer 1

Answer: Choice B)

an = 15 + a(n-1)

a1 = 250

============================================================

The variable "a" is used to represent the terms. Since we have infinitely many terms to worry about, we won'd use "b, c, d, etc" for the other terms or else we'd run out of letters. So instead, we just stick a number next to "a" to help keep track of the terms

a1 = first term, a2 = second term, a3 = third term, etc

The first term is 250 because Chenoa starts off with $250, so a1 = 250. The answer is between A and B at this point.

The recursive step is how we generate each term. In plain english, the recursive step would be "add 15 to each term to get the next term". In an informal equation, it would look like this

term = (previous term) + 15

So that is why the nth term is

`a_n = 15 + a_(n-1)`

which means "to get the nth term, we add 15 to the previous (n-1)st term"

This is why choice B is the answer