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fk378
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Homework Statement
Prove by an example, that we can find 3 groups E c F c G, where E is normal in F, F is normal in G, but E is not normal in G.
(c denotes "contained in")
Consider:
G=A_4
F={Id, (12)(34), (13)(24), (14)(23)} and
E={Id, (12)(34)}
The Attempt at a Solution
I want to use the fact that A_4 is the kernel of S_4 so automatically it is normal in S_4. But how is F related to S_4?