Question

Which is the radius of a circle whose equation is (x + 1)2 + (y - 1)2 = 25?
A 30
B 25
C 5
D 4
Answer and explanation please.

Answer 1

Equation of a circle is of the form:
(x-a)^2 + (y-b)^2 = r^2
Where (a,b) is the center and r is the radius.

In this case, 25 is r^2. Therefore, r = 5.

Answer 2

Thanks for the explanation.