A) 3x²-5x-28. The area of the rectangle with length 3x+7 and width x-4 can be represented as 3x²-5x-28.
The equation to find the area of the rectangle is simply A = l * w. This means that the area of a rectangle is equal to the product of its length (l) by its width (w), or of its length by its width.
A = w*l
A = (3x + 7)(x -4) = (3x)(x) + (3x)(-4) + (7)(x) + (7)(-4)
A = 3x² - 12x + 7x - 28
A = 3x² -5x - 28
