Question

Abbie decides to start doing crunches as part of her daily workout. She decides to do 15 crunches the first day and then increase the number 4 each day after that. Write an explicit formula for the number of crunches Abbie will do on day n.

Answer 1

For this case, the first thing we must do is define a variable.
We have then:
n: number of days.
We now write the explicit formula that represents the problem.
We have then:
an = 4n + 15
Where,
15: crunches the first day
4: increase the number 4 each day
Answer:
An explicit formula for the number of crunches Abbie will do on day n is:
an = 4n + 15