Chapter 9 - Quadratic Functions and Equations - 9-8 Systems of Linear and Quadratic Equations - Practice and Problem-Solving Exercises - Page 585: 17

Days 0 and 152 had the same number of sales Day 0 had 20 units sold of each Day 152 had 7296 units of each sold

$y=48x+20$ $y=-x^2+200x+20$ $-x^2+200x+20 =48x+20$ $-x^2+200x+20-48x-20=48x+20-48x-20$ $-x^2+152x =0$ $x(-x+152)=0$ $x=0$ $-x+152=0$ $-x+152+x=0+x$ $152=x$ $y=48*x+20$ $y=48*152+20$ $y=7296+20$ $y=7316$