Chapter 9 - Quadratic Functions and Equations - 9-6 The Quadratic Formula and the Discriminant - Practice and Problem-Solving Exercises - Page 572: 22

252.5 feet

$-.004x^2+x+2.5 = y$ $x=(-b± \sqrt {b^2-4ac})/2a$ $x=(-1± \sqrt {1^2-4*-.004*2.5})/2*-.004$ $x=(-1± \sqrt {1+.04})/-.008$ $x=(-1± \sqrt {1.04})/-.008$ $x=(-1±1.019)/-.008$ $x=(-1+1.019)/-.008$ $x=.019/-.008$ $x=19/-8 = -19/8$ (a negative distance is not valid in this problem) $x=(-1-1.019)/-.008$ $x=-2.019/-.008$ $x=-2019/-8 = 252.475$