Question

(G,12,1 point) The equation (x - 1)2 + (- 9)2 = r2 represents circle A. The point (3,9) lies on the circle. What is r, the length of the radius of circle A? O A. 4 O B. 2 O c. 5 O D. 10

Answer 1

B. 2

Step-by-step explanation:

If the point (3, 9) lies on the circle, we can replace the value of x by 3 and the value of y by 9 and solve the initial equation for r, so:

(x - 1)² + (y - 9)² = r²

(3 - 1)² + (9 - 9)² = r²

2² + 0² = r²

2² = r²

2 = r

Therefore, the length of the radius of circle A is 2.