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Answer:
4. b
5. a
Explanation:
4. The radius is the distance between the center (-6, -8) and the point on the circle (0, 0). The square of that is given by ...
r^2 = (-6-0)^2 +(-8-0)^2 = 36 +64 = 100
Only one of the offered choices has an r^2 value of 100: Choice B.
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5. The center and the point are on the same line (y=9), so the radius is the difference of x-coordinates: r = 5-2 = 3. The center is given as (h, k) = (5, 9).
The form of the equation of a circle is ...
(x -h)^2 +(y -k)^2 = r^2
Filling in the given values, the equation is ...
(x -5)^2 +(y -9)^2 = 9 . . . . matches choice A