Question 3 Move the center of the circle vertically so it lies above and then below the x-axis. How does the equation of the circle change as the center crosses
the x-axis?

 The variable k changes as the center of the circle moves vertically. The sign of k is positive when the center is below the x-axis and negative when it is above the x-axis. The sign of the variable k flips when the center moves across the x-axis.

Step-by-step explanation: plato/edmentum answer!

hope this helps! :)

step-by-step explanation:

points a and b are equidistant from the desired line, so the line you find by using them will go through point r.

using points other than a and b will give the desired line only if they are equidistant from r. if they are randomly located, the perpendicular line you create will not necessarily go through point r, hence will not be a solution to the problem.