You know that the length and the width of the rectangular backyards are:
Knowing the coordinates of the vertices of the rectangle, you can plot them on a Coordinate Plane and draw the rectangle. Notice that the vertices are:
See the picture below:
According to the information given in the exercise, a circular flower garden is dug to be exactly in the center of the backyard. The radius of this circle is:
If you draw the diagonals of the rectangle, you can find its center and therefore, the center of the circle. See the picture below:
Now you know the center of the circle.
By definition, the equation of a circle is:
Where "r" is the radius of the circle and its center is:
Since you already know the center of the circular flower garden and its radius, you only need to substitute values into the equation and simplify:
Therefore, the answer is: