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thoughtinknot
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Homework Statement
Let [itex]\mathbb{R}[/itex]*=[itex]\mathbb{R}[/itex]\{0} with multiplication operation. Show that [itex]\mathbb{R}[/itex]*=[itex]\mathbb{I}[/itex]2 ⊕ [itex]\mathbb{R}[/itex], where the group operation in [itex]\mathbb{R}[/itex] is addition.
Homework Equations
Let {A1,...,An}[itex]\subseteq[/itex]A such that for all a[itex]\in[/itex]A there exists a unique sequence {ak} such that a=a1+...+an where ak[itex]\in[/itex]Ak for all k, then A=A1⊕...⊕An
The Attempt at a Solution
Since [itex]\mathbb{I}[/itex]2={-1,1} I don't think I can show that every a*[itex]\in[/itex][itex]\mathbb{R}[/itex]* can be expressed in a unique way. For example let a+=a*+1 and a-=a*-1, then a*=a+-1=a-+1. Am I defining the cyclic group of order 2 wrong? I'm not that sure about direct sums, our prof spent 5 minutes on them and 40% of our assignment involves them :S
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