Isomorphism between $Z[X,Y ]/(2Y−1)$ and $Z[frac{1}/{2}][X]$

Hi I been trying to proof that $Z(X,Y )/(2Y−1)$ is isomorphic to $Z({1}/{2})(X)$ where$Z({1}/{2})$= $frac{a}{2^n} : a ∈ Z, n ∈ N, n ≥ 0$