Chapter 4 Quadratic Functions and Factoring - 4.8 Use the Quadratic Formula and the Discriminant - 4.8 Exercises - Problem Solving - Page 298: 70c

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From the given equation, we know: $a=-\frac{1}{640}\\b=\frac{1}{4}\\c=20$ The x-coordinate of the vertex is: $x=-\frac{b}{2a}=\frac{\frac{1}{4}}{-\frac{2}{640}}=80$ Thus, the motorcyclist travels from $x=0$ to the maximum height at $x=80$. The horizontal distance traveled is $80-0=80$ ft