The quantity demanded x for a certain brand of MP3 players is 100 units when the unit price p is set at $80. The quantity demanded is 1100 units when the unit price is $40. Find the demand equation.

p =

Answer:p = (2100 - x) / 25

Step-by-step explanation:

According to the law of demand, when the price, p of the brand of MP3 players is is high, the quantity, x of the brand of MP3 players demanded would be low and when the price, p of the brand of MP3 players is is low, the quantity, x of the brand of MP3 players demanded would be high.

To derive the demand equation, we would apply the slope intercept form of equation which is expressed as

y = mx + c

Where

m = slope

c = intercept

The slope, m would be

(y2 - y1) / (x2 - x1)

Slope = (1100 - 100) / (40 - 80) = 1000/-40

Slope = - 25

To find the y intercept, we would substitute m = - 25, y = 1100 and x = 40 into y = mx + c. It becomes

1100 = - 25 * 40 + c

1100 = - 1000 + c

c = 1100 + 1000 = 2100

y = - 25x + 2100

Therefore, the demand equation is

x = - 25p + 2100

25p = 2100 - x

p = (2100 - x) / 25