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+2y inches, the other side should be x^2+6xy-5y^2 inches. Write an algebriac expression for the area of such a whiteboard, simplify it and use correct units with the solution.
(x+2y)(x^2 + 6 xy -5 y^2)
= x(x^2 + 6 xy -5 y^2)+2y(x^2 + 6 xy -5 y^2)
= x^3+6x^2y-5xy^2+2x^2y+12xy^2-10y^3
= x^3 + 8x^2y +7xy^2 -10y^3 square inches