Cryptography, Algorithms, Public Key Cryptography.
How? Consider what can g be like to guarantee the existence of x within itself. It must contain x(trivial), its inverse 1/x (since closed under multiplication), identity 1(same reason) and all derived from x and 1/x such as x², x³, … and 1/x², 1/x³,… g = { …, 1/x³, 1/x², 1/x, 1, x, x², x³, … } Note