Question

The equation (x − 5)2 + (y + 3)2 = r2 represents circle T. The point S(-1,6) lies on the circle. What is r, the length of the radius of circle T?

Answer 1

r = 2.4

Explanation:

First of all, note that point S(-1,6) corresponds to S(x,y), therefore:

x = -1

y = 6

Now putting the value of x and y into the equation: (x − 5)2 + (y + 3)2 = r²

(x − 5)2 + (y + 3)2 = r²

(-1 − 5)2 + (6 + 3)2 = r²

(-6)2 + (9)2 = r²

-12 + 18 = r²

6 = r²

r = √6 = 2.4

∴ r = 2.4