Since it is linear, we can assume a function of the form:
[tex]y(x)=mx+b[/tex]Where:
m = Slope = rate of growth
b = y-intercept
So:
[tex]\begin{gathered} x=2002,y=142 \\ 142=2002m+b_{\text{ }}(1) \\ ----------- \\ x=2007,y=255 \\ 255=2007m+b_{\text{ }}(2) \end{gathered}[/tex]Using elimination method:
[tex]\begin{gathered} (2)-(1) \\ 255-142=2007m-2002m+b-b \\ 113=5m \\ m=\frac{113}{5}=22.6 \end{gathered}[/tex]So:
Replace m into (1):
[tex]\begin{gathered} 142=2002(22.6)+b \\ b=-45103.2 \end{gathered}[/tex]The linear equation which represents this model is:
[tex]y=22.6x-45103.2[/tex]The approximate rate of growth per year from 2002 to 2007 is 22.6 million
the expected number of people to have phones in:
[tex]\begin{gathered} x=2010 \\ y=22.6(2010)-45103.2 \\ y\approx323 \end{gathered}[/tex][tex]\begin{gathered} x=2015 \\ y=22.6(2015)-45103.2 \\ y\approx436 \end{gathered}[/tex][tex]\begin{gathered} x=2020 \\ y=22.6(2010)-45103.2 \\ y\approx549 \end{gathered}[/tex]323 million of people will have phones in 2010
436 million of people will have phones in 2015
549 million of people will have phones in 2020
