Answer:
20x^2 - 4x - 16
Explanation:
Area of a rectangle = Length * Width
Area = (5x + 4)(4x - 4)
Expand the double brackets using the FOIL method (First, Outer, Inner, Last), combine the terms and simplify:
F: 5x * 4x = 20x^2
O: 5x * -4 = -20x
I: 4 * 4x = 16x
L: 4 * -4 = -16
20^2 - 20x + 16x - 16
20x^2 - 4x - 16