Question 679397: In the year 2010, there were 200 million land line customers and in 2011, there were 196 million land line customers.
In the year 2010, there were 86 million cell phone customers and in 2011, there were 106 million cell phone customers. For both land line and cell phone customers, the number of customers is linearly related to the year.
A. Find a linear equation that models the number of land line customers, y(in millions), x years from 2010.
B. Find a linear equation that models the number of cell phone customers, y(in millions), x years after 2010.
C. Use the equations from parts A and B to determine the year in which the number of land line customers and the number of cell phone customers will be the same.
Answer by DrBeeee(684)   (Show Source):
You can put this solution on YOUR website! Let L = the number in millions of landlines.
Let x be the number of years, starting at x = 0 in 2010
Then the landline equation is
(A) L = -4x + 200, as it is decreasing 4 million a year, starting w/200 million in 2010.
Let W = the number in millions of wireless phones.
Then the wireless equation is
(B) W = 20x + 86, as it is increasing by 20 million a year, starting at 86 million in 2010.
To find the year they are the same, set (A) = (B), and get
(1) -4x + 200 = 20x + 86 or
(2) 24x = 114 or
(C) x = 4 and 9/12 years
They will be equal on October 1, 2014.
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