Question 175071
The formula for the area of a rectangle is length * width.  So, the area here is:

(2x - 1) * (x + 2)

Using FOIL:

(2x * x) + (2x * 2) + (-1 * x) + (-1 * 2)

2x^2 + 4x - x - 2

2x^2 + 3x - 2

So, your function is A(x) = 2x^2 + 3x - 2