# writing equations in point-slope forms

#### stephany

##### New member
a contruction company charges $15 per hour for debris removal plus a one-time fee for the use of a trash dumpster. The total fee for 9 hours of service is$195
write ther point-slope form of an equation to find the total fee y for any number of hours x.

#### mmm4444bot

##### Super Moderator
Staff member
stephany said:
… write [the] point-slope form of an equation [and then solve that equation for] the total fee y for any number of hours x.

If I want to find a formula to give me y for any number of hours that I choose for x, then I want the slope-intercept form.

y = m * x + b

There are different ways to find b, but the instruction calls for first writing the point-slope form (this does not require knowing the value of b), followed by solving the point-slope form for y.

In this exercise, the slope is the hourly rate. You're told that y increases by \$15 every time x increases by 1 hour. (Have you heard of rise-over-run? 15/1)

You know the coordinates of a point on the graph of the line because y = 195 when x = 9 is given.

If you do not know the point-slope form of a line, then try looking it up in your textbook.

It's the form we use to write the equation of a line when we know the slope and the coordinates of one point.

After you write the point-slope form using the given slope and xy-coordinates, then solve it for y.

Please show your work if you need more help with this exercise.

Staff member