Precalculus (6th Edition) Blitzer

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

Chapter 1 - Section 1.9 - Distance and Midpoint Formulas; Circles - Exercise Set - Page 281: 73

Answer

The given standard form of the equation to the set of points $\left( -2.4,\ -2.7 \right)$ that could be the epicenter of the quake which is 30 miles from the university is ${{\left( x+2.4 \right)}^{2}}+{{\left( y+2.7 \right)}^{2}}=900$.

Work Step by Step

Suppose that $\left( x,\ y \right)$ are the set of points that represent the epicenter. And also the distance between the university and the epicenter is 30 miles. The distance formula to find the distance between the two points is shown below: $d=\sqrt{{{\left( {{x}_{2}}-{{x}_{1}} \right)}^{2}}+{{\left( {{y}_{2}}-{{y}_{1}} \right)}^{2}}}$ Let ${{x}_{2}}=x\ ,\ {{x}_{1}}=-2.4,\ {{y}_{2}}=y\,\,\text{ and }\,\,{{y}_{1}}=-2.7$ and use the values in the distance formula as given below: $\begin{align} & 30=\sqrt{{{\left( x-\left( -2.4 \right) \right)}^{2}}+{{\left( y-\left( -2.7 \right) \right)}^{2}}} \\ & {{30}^{2}}={{\left( x-\left( -2.4 \right) \right)}^{2}}+{{\left( y-\left( -2.7 \right) \right)}^{2}} \\ & 900={{\left( x+2.4 \right)}^{2}}+{{\left( y+2.7 \right)}^{2}} \end{align}$ or ${{\left( x+2.4 \right)}^{2}}+{{\left( y+2.7 \right)}^{2}}=900$
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