A student forms a box from a 10 in. by 15 in. piece of cardboard by cutting a square with side length x out of each corner and folding up the sides. How do you write and simplify an expression for the area of the base of the box?
The base of the box is the rectangle made up of the dashed lines in the image.
Thus the length of the base is
The area of the base is length*width
Multiplying out gives
In standard form this is