Question

What is the radius of the circle x2 + y2 -1=0?

Answer 1

Answer: 1

Explanation:

rewrite x^2 + y^2 -1 = 0 as x^2 + y^2 = 1

the 1 on the right hand side of the equation is equal to the radius squared

1 = r^2

r = 1

Answer 2

radius = 1

Explanation:

x^2 + y^2 -1=0

Add 1 to each side

x^2 + y^2 -1+1=0+1

x^2+y^2 = 1

This is written in the form

(x-h)^2 + (y-k)^2 = 1^2 where (h,k) is the center and r is the radius

The center is (0,0) and the radius is 1