A school designer wants to create a whiteboard with the optimal dimensions to enhance learning. It is determined that if one side of the whiteboard is x + 5y inches, the other side should be x^2+3xy-4y^2 inches. Write an algebraic expression for the area of such a whiteboard, simplify it, and include correct units with your solution
area = length x width
= (x+5y)(x^2 + 3xy - 4y^2)
expand, and collect like terms.