Question

Write the equation of the circle whose center is at the origin and whose diameter is 12.

Answer 1

x^2 + y^2 = r^2 is the general formula for a circle with the center in [0,0]
Thus,
\[x^2 + y^2 = 12^2\]
\[x^2 + y^2 = 144\]

Answer 2

\[x^2+y^2+z^2=36\]

Answer 3

OR
\[x^2+y^2=36\]

Answer 4

the general form a a circle centered at \((a,b)\)\[(x-a)^2+(y-b)^2=r^2\]

Answer 5

This was (a little bit) of a trick question. They tell you the diameter is 12.
But you need the radius, which is 1/2 of the diameter. The radius is 6