Question

Which is the radius of a circle whose equation is (x + 1)2 + (y - 1)2 = 25?
30
25
5
4
.

Answer 1

5

Answer 2

How did you get that?

Answer 3

(x+1)^2 +(y-1)^2=5^2 is the standard form of an equation of a circle with centre (-1,2) and radius 5. Try to convert any equation of a circle to this form and one can get the radius and centre.