College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 2 - Section 2.4 - Circles - 2.4 Assess Your Understanding - Page 186: 30

Answer

(a) The circle has a center (3,-1) and a radius of 1 unit long. (b) See below. (c) The only x-intercept is $(3,0)$. There are no y-intercepts.

Work Step by Step

First, we need to make sure that the equation is in standard form $(x-h)^2+(y-k)^2=r^2$ In this case, we need to complete the square to achieve the standard form: $x^2+y^2-6x+2y+9=0$ $x^2-6x+y^2+2y=-9$ $x^2-6x+(\frac{6}{2})^2+y^2+2y+(\frac{2}{2})^2=-9+(\frac{6}{2})^2+(\frac{2}{2})^2$ $(x-3)^2+(y+1)^2=-9+9+1$ $(x-3)^2+(y+1)^2=1$ $(x-3)^2+(y+1)^2=1^2$ Now we can find the center (h,k) and the radius. The x-intercepts are all points of a graph when y=0: $(x-3)^2+(0+1)^2=1$ $(x-3)^2+1=1$ $(x-3)^2=0$ $\sqrt{(x-3)^2}=\sqrt0$ There is only one x-intercept: $x-3=0\rightarrow x=3$ The y-intercepts are all points of a graph when x=0: $(0-3)^2+(y+1)^2=1$ $9+(y+1)^2=1$ $(y+1)^2=-8$ $\sqrt{(y+1)^2}=\sqrt{-8}$ Taking the square root of a negative number is not possible; therefore, the graph doesn't intercept the y-axis at any point.
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