What is the difference in the areas of a square and rectangle if the rectangle has side lengths 4 less and 4 more than a square? Use algebra or a geometric model to compare the areas and justify your answer.
Let the side of the square = x
Then let the sides of the rectangle be x - 4 and x + 4
Area of square = x^2
Area of rectangle = ( x + 4) ( x - 4) = x^2 - 16
Difference in areas x^2 - ( x^2 - 16) = 16