How to express in pesos the manufacturer's weekly profit as a function of x?

Question

A clock manufacturer can produce a certain clock at a cost of P398 per clock. It is estimated that if the selling price of the clock is x pesos, then the number of clocks sold per week is 565-x.

Answer 1

x = selling price per clock

565-x = # clocks sold

 

Revenue is number of clocks sold times selling price per clock = (565-x)x

Cost is 398 times number of clocks = 398(565-x)

 

Profit = Revenue - Cost

P(x) = (565-x)x - [398(565-x)]

P(x) = 565x - x² - 398(565) + 398x

P(x) = -x² + 963x - 224870