Need to create a formula

Question

The number of cell phone subscribers in the U.S. reached 256 million in 2008, up
from 34 million in 1995. Find the equation of the line that depicts this info and
use the equation to estimate the number of cell phone subscribers in the U.S. in
2012.

Answer 1

Hi Alyssa!

 

I am sure you remember that the equation for a line is y=mx+b. However there is another equation that might be more helpful in this situation! That is:

 

Y - Y₁ = m(X-X₁) 

 

We also know that the slope of a line is "rise" divided by "run":

 

m = (Y₂-Y₁) / (X₂-X₁)

 

Now notice that your problem gives you two coordinates in the form of (X, Y) = (Year, Subscribers) where X=Year and Y=Subscribers. Take your two points and find the slope of the line. Now take your slope and one pair of points and plug it into the equation for the line. Now you have an easy-to-use equation that will tell you whatever you want to know!

 

The problem asks for the number of subscribers in 2012... so take your new equation and plug 2012 into X and you are just about done!! Just solve for Y and you found your answer!!

 

Great question! Keep up the good work!!

 

~~Michael S.