Question 543336
Profit = $0.15 × number of e-readers sold – $28
Or, assuming x = the number of e-readers sold, this would be the same regression equation:
Profit = 0.15x – 28
In this case, the values are given in thousands (i.e., the cost of making an individual e-reader will be $150 [0.15 × 1,000], with $28,000 [28 * 1,000] in constant charges). 
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To graph this equation y = .15x-28, where y is the profit, x = no.of items all values in 1000's
Make a table of values from this equation from x=10 items to x=1000 items
substitute for x and find y
  x | y
--------
 10 |-26.5; a loss
 100|-13
 200|+2; beginning to make a profit at 200 units
 500| 47
1000|122
Plot these, should look like this
{{{ graph( 300, 200, -100, 1100, -50, 150, .15x-28, 47) }}}
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For example if x = 500 units, the equation
y = .15(500) - 28
y = 75 - 28
y = 47, (which is a profit of $47,000), where the green line crosses the red line
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Did this help un-confuse you in this?