In Example 1, change (y + 2)² to (y + 1)².

Data from Example 1

The equation (x − 1)² + (y + 2)² = 16 represents a circle with center at (1,−2) and a radius of 4. We determine these values by considering the equation of the circle to be in the form of Eq. (21.11) as

Note carefully the way in which we found the y-coordinate of the center. We must have a minus sign before each of the coordinates. Here, to get the y-coordinate, we had to write +2 as −(−2). This circle is shown in Fig. 21.31.

(x - 1)2 + [y - (-2)]2 = 42 = = = coordinates of center form requires signs radius -