Posted by Anonymous on .
The standard form of a circle is Ax^2+Cy^2+Dx+Ey+F=0.
Write the equation for the circle:
Center (1,2), point on the circle (2,1).
Okay, I've always put circles in the form (xh)^2+(yk)^2=0. I got this:
r^2=(x1)^2+(y2)^2
then I substitute the point to find the radius:
r^2=(3)^2+(3)^2
r^2=18
So the answer I got is
18=(x1)^2+(y2)^2.
...So what's standard form, and can I change it from my answer to that?
Thx

Math 
Reiny,
expand and bring all terms to the left side.