Write the rule from a situation, step by step
A gym charges $25 to join and $12 a month.
The question
$40 to rent, then $10 a day. Write y in terms of x, where x is the number of days.
Find the start and the rate, then write the rule
b=40
m=10
y = 10x + 40
- "$40 to rent, then $10 a day". Two numbers, and they do different jobs. Find the one that is there before anything happens — that is b, the start.
- The other number goes with every one of the days, so it is m, the rate. It is added each time, so m is 10.
- Put them into y = mx + b in that order — the rate multiplies x, the start stands alone.
How it works.
- 01
"$40 to rent, then $10 a day". Two numbers, and they do different jobs. Find the one that is there before anything happens — that is b, the start.
- 02
The other number goes with every one of the days, so it is m, the rate. It is added each time, so m is 10.
- 03
Put them into y = mx + b in that order — the rate multiplies x, the start stands alone.