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: 35

Answer

(a) The circle has a center (-2,0) and a radius of 2 units. (b) See below. (c) There are two x-intercepts: (-4,0) and (0,0). There is only one y-intercept: (0,0).

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: $2x^2+8x+2y^2=0$ $2(x^2+4x+y^2)=0$ $x^2+4x+y^2=0$ $x^2+4x+(\frac{4}{2})^2+y^2=(\frac{4}{2})^2$ $(x+2)^2+y^2=4$ $(x+2)^2+y^2=2^2$ Now we can find the center (h,k) and the radius. The x-intercepts are all points of a graph when y=0: $(x+2)^2+0^2=4$ $(x+2)^2=4$ $\sqrt{(x+2)^2}=\sqrt4$ There are two x-intercepts: $x_1+2=-2\rightarrow x_1=-4$ $x_2+2=2\rightarrow x_2=0$ The y-intercepts are all points of a graph when x=0: $(0+2)^2+y^2=4$ $4+y^2=4$ $y^2=0$ $\sqrt{y^2}=\sqrt{0}$ There is only one y-intercept: $y=0$
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