What is the general form of the equation of a circle with a center at the origin and a radius of 9?

2 Answers
Dec 26, 2015

Answer:

#x^2+y^2=81#

Explanation:

Any general circle centred at #(a,b)# and with radius #r# has equation #(x-a)^2+(y-b)^2=r^2#

So in this case since the centre is the origin, it implies that #a=b=0#, and the radius #r=9 => r^2=9^2=81#.

Thus the equation reduces to #x^2+y^2=81#.

Dec 26, 2015

Answer:

#x^2 + y^2 = 9^2#

Explanation:

General Equation of a circle:
#(x-a)^2+(y-b)^2=r^2#
where (a,b) are the coordinates of center and 'r' is the radius
since in you question center lies on origin and the radius is 9
therefore, (a,b) = (0,0) and r=9
hence, #x^2 + y^2 = 9^2#