Let me refer you to:
http://www-users.math.umd.edu/~karpuk/chap3solns.pdf
Page 2, ex. 4
Can you please explain the following step:
tb=f(s')b=s'b
Why f(s')=s' ?
Thanks
Let me refer you to:
http://www-users.math.umd.edu/~karpuk/chap3solns.pdf
Page 2, ex. 4
Can you please explain the following step:
tb=f(s')b=s'b
Why f(s')=s' ?
Thanks
Hint: We have a map $f:A\rightarrow B$. This makes $B$ into an $A$-module. What is the definition of "$ab$", for $a\in A$ and $b\in B$?