The operation Δ is defined for all nonzero x and y by x Δ y ~$=x+\frac{x}{y}$~ .  If a > o, then 1 Δ (1 Δ a) =

a

a+1

~$\frac{a}{a+1}$~

~$\frac{a+2}{a+1}$~

~$\frac{2a+1}{a+1}$~