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: 32

Answer

(a) The circle has a center (-0.5,-0.5) and a radius of 1 unit. (b) See below. (c) There are two x-intercepts: (-1.37,0) and (0.37,0). There are two y-intercepts: (0,-1.37) and (0,0.37).

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: $x^2+y^2+x+y-0.5=0$ $x^2+x+y^2+y=0.5$ $x^2+x+(\frac{1}{2})^2+y^2+y+(\frac{1}{2})^2=0.5+(\frac{1}{2})^2+(\frac{1}{2})^2$ $(x+0.5)^2+(y+0.5)^2=0.5+0.25+0.25$ $(x+0.5)^2+(y+0.5)^2=1$ $(x+0.5)^2+(y+0.5)^2=1^2$ Now we can find the center (h,k) and the radius. The x-intercepts are all points of a graph when y=0: $(x+0.5)^2+(0+0.5)^2=1$ $(x+0.5)^2+0.25=1$ $(x+0.5)^2=0.75$ $\sqrt{(x+0.5)^2}=\sqrt{0.75}$ There are two x-intercepts: $x_1+0.5=-\sqrt{0.75}\rightarrow x_1=-\sqrt{0.75}-0.5\approx-1.37$ $x_2+0.5=\sqrt{0.75}\rightarrow x_2=\sqrt{0.75}-0.5\approx0.37$ The y-intercepts are all points of a graph when x=0: $(0+0.5)^2+(y+0.5)^2=1$ $0.25+(y+0.5)^2=1$ $(y+0.5)^2=0.75$ $\sqrt{(y+0.5)^2}=\sqrt{0.75}$ There are two y-intercepts: $y_1+0.5=-\sqrt{0.75}\rightarrow y_1=-\sqrt{0.75}-0.5\approx-1.37$ $y_2+0.5=\sqrt{0.75}\rightarrow y_2=\sqrt{0.75}-0.5\approx0.37$
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