A circle's equation consist on the following expression: , where r is the magnitude of the radio, and (a,b) are the coordenates of the center of the circle.
In this case, a=2 and b= - 3, because the circle is centered in (x,y)=(2, - 3).
The radio, which is the distance between the center of the radio to any point in its border, equals r=2 (because of the scale of the graphic, in this case two squares of the grid equal 2 units, then r=2).
Finally, using the previous information to replace in the equation , where the fact that r=2 and was used.
If the teacher has 1/2 of an eraser, and she divides it into 2 pieces to give 1 to each of her students, she gives (1/2) / 2 = (1/2) * (1/2) = 1/4 of the eraser to each student.
, where r is the magnitude of the radio, and (a,b) are the coordenates of the center of the circle.
, where the fact that r=2 and
was used.