Question

I need to write an equation that relates the monthly charge C, in dollars, to the number of x of the kilowatt-hours used in each month. the fixed monthly charge is $5.25 plus 6.787 cents per kilowatt-hours, then I have to graph the equation. Can someone please tell me if I would use y=mx+b equation for this.

Answer 1

5.25 is the fixed cost, and 6.787 per kilowatt hour could be written like 6.787x right? since x is the number of kilowatt hours used.

So, the monthly charge would be:
C=6.787x+5.25

Answer 2

ok... that's what I was thinking. How would I graph that though? Thank you for helping me :)

Answer 3

would I have to plug in different hours into the x variable to get the different points on the line?

Answer 4

You could do that, since you know its a line and its in the form y=mx+b where b is the y intercept you already have a point (0,5.25)

And then plot another point and just draw a line through the two

Answer 5

oh.... you have no idea how helpful you have been. I really appreciate your help. Would you be willing to help me with one more question :)

Answer 6

You're welcome. And i could try =D

Answer 7

ok.. thank you. one care rental firm charges $125 for a week-end rental and gives unlimited mileage. A second firm charges $95 plus $.20 a mile. For what range of miles driveen is the second firm cheaper. It's an inequality problem. My issue is I never no which equation to use and when. Would I be using the y=mx+b again?

Answer 8

Hmm, lets start by setting up equations for each company.

The first would be just cost=125

the second would be cost=.20m+95 where m is miles.

agreed?

Answer 9

yes... so then I would plug in like 2 for m and see if it's less at that point?

Answer 10

Oh no you can solve this, you want to find when the second company's cost will be less than the first, so:

125>.20m+95

now just solve for m

Answer 11

ok... so I get a little confused here. should I be getting m alone?

Answer 12

Yep. Solve for m like you would in an equation

Answer 13

ok.... thank you so much. I hope someday this will come a little easier to me :) like accounting does.

Answer 14

Ha maybe. What did you get for your answer?

Answer 15

still working on it. Would you like me to let you know what I get.

Answer 16

to get m alone do I divide .20 from both sides?

Answer 17

sorry it really doesn't come easy to me.... no matter how much I read.

Answer 18

Well i would subtract 95 from both sides first so you get
30>.20m

Then divide both sides by .20

Answer 19

so you subtract 95 from 125 and 95 and then divide it by .20

Answer 20

Yep. What do you get?

Answer 21

so would the answer be m= 150

Answer 22

or is it .00667

Answer 23

150>m

So for the second company to be cheaper than the first, you have to drive less than 150 miles.

Answer 24

ok... so I had it right just not putting in the right form

Answer 25

thank you for helping me :)

Answer 26

You're welcome

Answer 27

are you on alot.... :) for future reference of course.

Answer 28

Eh, sometimes. At least once every other day for a bit. I should be on for a while longer tonight if you need help with anything else

Answer 29

thank you :)