You should KNOW 

        1.  How to "complete the square" in a quadratic expression.
        2.  The formulas for the distance between two points and the midpoint of the line segment connecting them.
        3. The idea of the coordinate plane.
        4. That the graph of an equation in two variables x,y is the set of points in the plane whose coordinates (x,y) satisfy the equation. 

You should be ABLE TO

         1.  Complete the square in a quadratic expression. 
          2.  Find distances between and midpoints of pairs of points.
         3.  Find an equation for a circle from geometric information e.g. the center and diameter.
         4.  Find geometric information about a circle from its equation.