I know that we have to show (Φ(x))^2 = Φ(x) and that x is idempotent if x^2 = x, but I don't know where to go after that
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Given an idempotent x:
Φ(x) = Φ(x^2), since x = x^2
.......= Φ(x) Φ(x), since Φ is a ring homomorphism
.......= [Φ(x)]^2.
I hope this helps!
Φ(x) = Φ(x^2), since x = x^2
.......= Φ(x) Φ(x), since Φ is a ring homomorphism
.......= [Φ(x)]^2.
I hope this helps!