How do I write a formula to populate anything that is created in that week, it will add the Monday date of that week. 

For Example:
I have records for 10/7, 10/8, 10/10. I need the Starting Week of to be: 10/7 for all Dates. 
Then I need records for 10/14, 10/15, 10/16, etc. To be starting week of 10/14.

I also have the: WEEKNUM({Created Date}) formula, so if there is an easier way to turn that week number into the starting date of the week, I can use that as well.