You deck has an area of 128 square feet. after adding a section, the are will be s by the power of 2+128 square feet. draw a diagram of how this can happen. .

You are adding s^2 to your 128 ft^2.  s^2 is a common representation of a square.  So you could think of it as adding an area of a square of side "s" to your deck.

So one way of drawing it is to draw a rectangle with area 128 ft^2 and attaching a square to one of its side.  The square that is attached has a side lenght of "s."

Apples because you're getting more even though its a little more expensive its 1 1/3