Question

Consider the set X=R\{-1}. Define * on X by
x1 * x2= x1+ x2+ x1x2 ¥ x1,x2 € X.
i) check whether (X,*) is a group or not.
ii) Prove that x*x*x*....*x (n times)=(1+x)n -1¥n€N and x€X