Show that the random variables with the densities

f(x, y) = x + y

and

g(x, y) = (x + 1/2)(y + 1/2)

if 0 ≤ x ≤ 1, 0 ≤ y ≤ 1 and f(x, y) = 0 and g((x, y) = 0 elsewhere, have the same marginal distribution.