SOLUTION: Apple sold 55 million iPods in 2008, but as iPhones became more popular, that sales of iPods began to decrease. The number of iPods sold in 2011 was about 40 million. Write linear

Algebra ->  Finance -> SOLUTION: Apple sold 55 million iPods in 2008, but as iPhones became more popular, that sales of iPods began to decrease. The number of iPods sold in 2011 was about 40 million. Write linear       Log On


   



Question 1104909: Apple sold 55 million iPods in 2008, but as iPhones became more popular, that sales of iPods began to decrease. The number of iPods sold in 2011 was about 40 million. Write linear equation in slope-intercept form to model this decrease in sales. Let x stand for the number of yours after 2008 and ley y stand for the number of iPods sold, in millions.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You are given 2 points on the line:
( 0, 55 ) and ( 3, 40 )
Note that I say 2008 is +x+=+0+
and 2011 is +x+=+3+
The y-axis is in millions of ipods
-----------------------------------
Use the general point-slope formula
+%28+y+-+40+%29+%2F+%28+x+-+3+%29+=+%28+55+-+40+%29+%2F+%28+0+-+3+%29+
+%28+y+-+40+%29+%2F+%28+x+-+3+%29+=+15+%2F+%28-3%29+
+%28+y+-+40+%29+%2F+%28+x+-+3+%29+=+-5+
+y+-+40+=+-5%2A%28+x+-+3+%29+
+y+-+40+=+-5x+%2B+15+
+y+=+-5x+%2B+55+
---------------------------
check answer:
Does it go through ( 0,55 )?
+55+=+-5%2A0+%2B+55+
+55+=+55+
OK
Does it go through ( 3, 40 )?
+40+=+-5%2A3+%2B+55+
+40+=+-15+%2B+55+
+40+=+40+
OK