## Algebra 1: Common Core (15th Edition)

Published by Prentice Hall

# Chapter 9 - Quadratic Functions and Equations - 9-2 Quadratic Functions - Practice and Problem-Solving Exercises - Page 557: 31

#### Answer

50 dollars per phone

#### Work Step by Step

Allow x to be the number of additional phones that are sold. R = (price per phone)(number of phones sold) number of phones sold = 500 +20x price per phone = 75-x Multiply (500+ 20x)(75-x) together to get: R = 37500 +1000x -20x^2 Then, using the following equation, use the axis of symmetry formula to find the x coordinate that maximizes the revenue: x = -b/2a simplifies to: x= -1000/2(-20) simplifies to: x= 25 Once you have the value of x, plug it back into the equation 75 - x, which represents the price per phone. 75-25 =50 Therefore, the price should be 50 dollars per phone.

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