<PRE><B>Question 701268</B>
The quantity demanded for a certain brand of portable CD players is 200 units when the unit price is set at $90. The quantity demanded is 1200 units when the unit price is $40. Find the demand equation and sketch its graph. 
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You have two points: (90,200) ; (40,1200)
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slope = (1200-200)/(40-90) = -1000/50 = -20
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D(x) = -20x + b
Solve for &quot;b&quot;:
200 = -20*90 + b
b = 200 + 1800
b = 2000
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Equation:
D(x) = -20x + 2000 where x is the price per unit.
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Cheers,
Stan H.
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