## A simple Line question

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.

### A simple Line question

Rani is comparing the monthly costs from two internet service providers. #1 charges \$10 initially + \$.75 per hour #2 is \$5 initially and \$1 per hour!

How would i figure when the two lines which i already have in y=mx+b which are y=.75x+10 and y=1x+5. how do i figure out the coordinates without using a graph so algebraicly
Mason

Posts: 1
Joined: Mon Jan 26, 2009 2:10 am

### Re: A simple Line question

I presume you mean, when do the two lines cross (when do both equations have the same x and y values).

To solve it algebraically, set the first equation equal to the second equation (substitute '.75x + 10' into the y of 'y = x + 5') and solve for x. Then substitute x back into either of the equations to find out y.

DAiv
DAiv

Posts: 44
Joined: Tue Dec 16, 2008 7:47 pm

### Re: A simple Line question

I did this a chapter or two ago. The graphing is so long and boring! Algebraically is faster and easier! Since you have both as "y=", you can just do the two other sides equal to each other: 0.75x + 10 = x + 5. Then minus 0.75 from each side and minus 5 from each side: 5 = 0.25x. 0.25 = 1/4, so times by 4: 20 = x.

You can put 5 in for x in either one of the first equations, and this will give you y.

little_dragon

Posts: 188
Joined: Mon Dec 08, 2008 5:18 pm