JST17 3. 1b Completing the square and area

Topic:
Area, Square
Use the slider bars to set the values of then in the equation . How do you know that the blue regions in each diagram have equal area? How do you know that the shape on the right is square? How do you find the area of the yellow region? Why is this process called COMPLETING THE SQUARE? How is the process of completing the square helpful to solve the equation?