Find the center and radius of the circle x2+y2=16

The standard form of the equation of a circle is

(

x

-

a

)

2

+

(

y

-

b

)

2

=

r

2

where (a, b) are the coords of the centre and r, the radius.

x

2

+

y

2

=

16

is in this form

with a = b = 0 and r = 4

hence this circle has centre at the origin (0,0) and radius 4

The intercepts will therefore be (± 4,0) and (0, ± 4)