Intersection of finite-dominating subgroup with any subgroup whose product with it is the whole group is finite-dominating in it
Statement
Suppose is a group, is a Finite-dominating subgroup (?) of , and is any subgroup of such that . Then, is a finite-dominating subgroup of .
This statement can be interpreted as saying that the property of being a finite-dominating subgroup satisfies a weak variant of the transfer condition.
Proof
Given: is a finite-dominating subgroup, .
To prove: is finite-dominating in . In other words, if is a finite subgroup of , is conjugate in to a subgroup of .
Proof: Since is finite-dominating in , there exists such that . Since , we can write , with . Then, . Since , this yields .
By assumption, , so . Thus, we have found conjugating to a subgroup of .