math
posted by Garrick .
a circle with center at the point O(0,0) also has the point P(2,3) on it. The equation of this circle is?
and a second question:
A circle has a center of square root 5. The equation of this circle is?
Please help me.

the general equation of a circle with centre at (0,0) is
x^2 + y^2 = r^2
sub in your given point to find r^2 and you are done.
your second question makes no sense
the centre of a circle is a position, not a value.