Posted by **Anonymous** on Saturday, February 6, 2010 at 6:57pm.

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 (x-h)^2+(y-k)^2=0. I got this:

r^2=(x-1)^2+(y-2)^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=(x-1)^2+(y-2)^2.

...So what's standard form, and can I change it from my answer to that?

Thx

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