I have a hard time to show the following isomorphism anyone can help me with the type f : G-> Q^* .Show that the group

- G=Q∖{−1/2} with binary operation x∗y=x+y+2xy is isomorphic to Q∖{0} with multiplication.
- Find a subgroup H≤GH≤G so that G/H≅Z2G/H≅Z2 (the group with two elements)