The answer is below.
Work Step by Step
Of the larger shape, one side is x and one side is x+2. When you multiply these two values, you get $x^2 +2x$. However, you can also add the areas of the two smaller shapes. The area of one is $x^2$, and the area of the other is $2x$. These add to get $x^2 +2x$, which confirms that x(x+2) is actually $x^2 +2x$.