(a) Prove that in a group G, (i) identity element is unique. (ii) inv…

Previous year question for Discrete Mathematics.

Question

(a) Prove that in a group G,

(i) identity element is unique.

(ii) inverse of each element of G is unique.

(b) Prove that a non-empty subset H of a group G is a subgroup of G if and only if the following two conditions hold: (i) $ab \in H, \forall a, b \in H$ (ii) $a^{-1} \in H, \forall a \in H$.

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