I was looking at a paper, and I saw this claim,
It is obvious that if $H$ has finite index in $F_m$ then $H$ has non-trivial intersection with each of the non-trivial subgroups of $F_m$.
Why is this immediate?
I was looking at a paper, and I saw this claim,
It is obvious that if $H$ has finite index in $F_m$ then $H$ has non-trivial intersection with each of the non-trivial subgroups of $F_m$.
Why is this immediate?