7. Determine whether the given relation from the set R of real numbers to itself is a func- tion. . If so, is the function injective? Surjective? Find the range. Prove your answers. . If not, find the largest possible subset U of R on which the relation is a function, in the sense that 2n (U x R) is a function. (a) (8 points) = {(x,y)|x'+y=x} (b) (8 points) = {(x,y)Ix+ y