The general equation for a circle is where the center of the circle is (h, k) and the circle has a radius of r.

I won't even bother with the first one...

2)

We need to complete the square for both the x and y variables:

Now, . So looking at the first set of parenthesis we've got . Equating the linear coefficient of this expression and the one right above we see that , so . This means we want to add to to make it a perfect square since . But what we do to one side of the equation we need to do to the other. Thus:

Now to the y variable. The problem is identical and we find we need to add to both sides again:

So this circle has a center at and a radius of 1.

-Dan