Acircle has the order pairs (-1, 2) (0, 1) (-2, -1) what is the equation . show your work.

We know that:



is an equation of a circle.

When we substitute x and y (from the pairs we have), we'll get a system of equations:



and all we have to do is solve it for a, b and r.

There will be:



From equations (II) and (III) we have:



and from (I) and (II):



Now we can easly calculate a and b:



Finally we calculate :



And the equation of the circle is:

31/6= 19/6 19/6 *1/7=19/42