1. Modeling with Functions

Modeling functions kill me, my brain malfunctions when I try them. I can do easy ones but then they get really complicated. Help with this one would be appreciated.

You have a $70 coupon from the manufacturer good for the purchase of a cell phone. The store where you are purchasing your cell phone is offering a 40% discount on all cell phones. Let x represent the regular price of the cell phone. (a) Suppose only the 40% discount applies. Find a function f that models the purchase price of the cell phone as a function of the regular price x. (b) Suppose only the$70 coupon applies. Find a function g that models the purchase price of the cell phone as a function of the sticker price x.

2. (a) $\displaystyle f(x) = .6x$

(b) $\displaystyle g(x) = x - 70$

3. I guess I can see how you got $\displaystyle g(x)$ but I don't understand how you got $\displaystyle f(x)$. Could you explain how you got there?

4. when you get a 40% discount, you only pay 60% of the cost.