If commutativity of vector space is omitted, can we still use other axioms to prove the commutativity?

462 Views Asked by At

Here I am thinking of using $-(x+y)$ and show that it equals $-(y+x)$.

$-(x+y)=-x-y$ by distributivity

=$-x-y+0=...$ Here I don't know how to continue, could someone suggest?

1

There are 1 best solutions below

6
On BEST ANSWER

Yes this is possible even for a (left) module $M$ over a ring $R$ with a multiplicative identity $1$: $$(1+1)(x+y)=x+y+x+y$$ by the left distributive law. But also $$(1+1)(x+y)=2(x+y)=2x+2y=x+x+y+y.$$Cancelling $x$ and $y$ at both sides yields $x+y=y+x$, that is, $M$ must be an abelian group.