Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 1 - Graphs - 1.4 Circles - 1.4 Assess Your Understanding - Page 38: 44


${{\left( x-4 \right)}^{2}}+{{\left( y+2 \right)}^{2}}=9$

Work Step by Step

The standard equation of circle with center$(h,k)$ and radius $r$ is ${{\left( x-h \right)}^{2}}+{{\left( y-k \right)}^{2}}={{r}^{2}}$ The center of the circle is $(4,-2)$ The circle is tangent to the line $x=1$. Therefore, the radius is the distance from the point $(4,-2)$ to $x=1$. The distance of point $\left( x,y \right)$ from $x=a$ is $\left| x-a \right|$ Therefore, the distance of point $(4,-2)$ from $x=1$ is $\,|4-1|\,=\,3$ Therefore, the radius of the circle is $3$. This gives: ${{\left( x-4 \right)}^{2}}+{{\left( y+2 \right)}^{2}}=9$
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