Powershell script to retrieve members from several groups

Hello. Please bare with me as I am new to Powershell. After getting into it I can't believe that I haven't been using this longer! My problem is that I'm so far unsuccessful in writing a script that will list the members of multiple groups using Get-ADGroup. This is what my code looks like:

$ADgroups1=Get-ContentC:\Temp\ListofGroups1.txt

(

Get-ADGroup"$ADgroups1"-propertiesmembers).members |

-propertiesdisplayName,SamAccountName|Select-ObjectdisplayName,SamAccountName|

-append-filepathC:\temp\multiplADgroupmembers.txt

This is the error I get when I use that:

Get-ADGroup : Cannot find an object with identity:

When I specify just one group then it works perfect. It looks like this:

$ADgroup1="Group Name"

(Get-ADGroup-identity"$ADgroup1"-propertiesmembers).members |

-propertiesdisplayName,SamAccountName|Select-ObjectdisplayName,SamAccountName|

-append-filepathC:\temp\multiplADgroupmembers.txt

Again, I want to retrieve users from multiple groups. I'd also like to be able to label them according to their groups if possible. I truly appreciate all your help as I am new to this and would appreciate recommendations in literature to get a beginner like me to be an expert like you :).