Question

You joined an online coupon club. You earned 100 bonus points just by signing up. Each month you use the site, you earn another 10 points. Which equation best models the points you can earn?

Answer 1

100 + 10x (x=months)

Answer 2

So,

I'm assuming you want me to make a formula for figuring your points after any given month assuming that you use the site at least once a month and you don't spend your points.

After one month, you will have your base 100 points plus an additional 10 points.

100 + 10 = 110

After two months, you will have gained an additional 10.
110 + 10 = 120

We can put this into a function, where P is your points, and m is the number of months you use the site.

P(x) = 100 + 10m

So after 500 months, you will have:

P(x) = 100 + 10(500) = 5100 points!

This is identical with:
y = 100 + 10m

and

y = 10m + 100

So this can be graphed as a linear equation/function with a y-intercept of 100 and a slope of 10/1.