function P (x) = 740 - 39x

Question

2) Mattias has saved some money that he wants to spend to pay his money
mobile phone subscriptions. Every month he will pay the same amount. Mattias
calculates how much money he has left with the function P (x) =
740 - 39x which shows how much money he has left, P (x) in money, after x
months.
. a) How much money has he saved?
. b) What does 39 mean in the function expression?
. c) Calculate P (12) and explain what that means.
. d) Solve the equation P (x) = 500 and explain what it means. (Round off to integers.) How does this actually fit? Motivate.

Answer 1

Answer b) first:

presumably he pays $39 per month

 

then a)

presumably he has $740 saved

 

c)

p(12) = 740 - 39*12 ... you do the arithmetic...12 monthly payments means he has paid for a year and what does p(12) mean then?

 

d)

p(x) = 500 = 740 - 39x

subtract 500 from each side: 0 = 240 - 39x

add 39x to each side

39x = 240

x = 6 + a remainder---x is months--what has he done in 6 months?