Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter P - Section P.7 - Equations - Exercise Set - Page 109: 170

Answer

The solution of the equation $s=-16{{t}^{2}}+{{v}_{0}}t$ for $t$ is $t=\frac{{{v}_{0}}\pm \sqrt{v_{0}^{2}-64s}}{32}$.

Work Step by Step

Consider the equation $s=-16{{t}^{2}}+{{v}_{0}}t$. Subtract $s$ from both sides. $\begin{align} & s-s=-16{{t}^{2}}+{{v}_{0}}t-s \\ & 0=-16{{t}^{2}}+{{v}_{0}}t-s \\ & -16{{t}^{2}}+{{v}_{0}}t-s=0 \end{align}$ Use the quadratic formula $x=\frac{-b\pm \sqrt{{{b}^{2}}-4ac}}{2a}$ to solve the equation $-16{{t}^{2}}+{{v}_{0}}t-s=0$ where $x=t$, $a=-16$, $b={{v}_{0}}$ and $c=-s$. $\begin{align} & t=\frac{-{{v}_{0}}\pm \sqrt{{{\left( {{v}_{0}} \right)}^{2}}-4\left( -16 \right)\left( -s \right)}}{2\left( -16 \right)} \\ & =\frac{-{{v}_{0}}\pm \sqrt{{{\left( {{v}_{0}} \right)}^{2}}-64s}}{-32} \\ & =\frac{{{v}_{0}}\pm \sqrt{v_{0}^{2}-64s}}{32} \end{align}$ The solution of the equation is $t=\frac{{{v}_{0}}\pm \sqrt{v_{0}^{2}-64s}}{32}$.
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