product of a module by an ideal

2.2k Views Asked by At

I have a ring $R$, an ideal $I$ of $R$ and an $R$-module $M$. How does one define $IM$. Is it the set $\{im\ \vert\ i\in I, m\in M\}$ or is it the smallest module containing these elements?

1

There are 1 best solutions below

3
On

Assuming that $R$ is commutative, then we can proceed as in A&M page 19.

Let $I\subset R$ be an ideal, and let $M$ be an $R$-module. Then, $IM$ is the set of all finite sums $\sum r_ix_i$ where $r_i\in I$ and $x_i\in M$. This is of course a submodule of $M$.