Question

1-5. Find the coordinates of the center and the measure of the radius for a circle whose equation is, 1. (x-8)^2+(y+4)^2=12 2. (x+8)^2+(y-4)^2=81 3. X^2+(y-5)^2=9 4. (x+4)^2+(y+5)^2=64 5. (x-7)^2+(y-3)^2=144 6. Write the equation of a circle whose center is (0, -5) and radius is 7. 7. Write the equation of a circle whose center is (6, -1) and diameter is 12. 8. Write the equation of a circle whose center is (-2, 3) and radius is 4. 9. Find the radius of a circle whose center is (0,3) and a y-intercept of (0,7).

Answer 1

1. (8,-4), sqrt(12) = 2×sqrt(3)

2. (-8,4), 9

3. (0,5), 3

4. (-4,-5), 8

5. (7,3), 12

6. x^2 + (y+5)^2 = 49

7. (x-6)^2 + (y+1)^2 = 144

8. (x+2)^2 + (y-3)^2 = 16

9. (0-0)^2 + (7-3)^2 = r^2

0 + 16 = r^2

=> r = 4

Explanation:

remember, the general equating of a circle is

(x-h)^2 + (y-k)^2 = r^2