Thread: Normal subgroup

Let G be a group and let H<=G with [G:H]=2 show that H normal subgroup of G

Originally Posted by mathemanyak

Let G be a group and let H<=G with [G:H]=2 show that H normal subgroup of G

is a normal subgroup if and only if . Create the cosets . If then because partitions the set into two sets. If then and thus again because partitions the set into two sets.