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## Homework Statement

Prove that a direct sum of two or more field is never a field

## Homework Equations

F X G = {(f,g): f in F, g in G}

## The Attempt at a Solution

I know that I need to prove FXG is Abelian group under addition, and FXG - {0,0} is an Abelian group under mult.

And for mult,

I know I need to check 1) mult identity, 2) closure, 3) commutative, 4) mult inverse, 5) associativity

I have problem proving mult inverse,

let a1, a2, b1, b2 be elements in F XG - {0,0}, such that (a1,b1)*(a2,b2) = (a1a2, b1b2)

so (a1a2, b1b2) ^-1 = (1/(a1a2), 1/(b1b2)) which is not in FXG - (0,0)

Is this right?

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