ADDDATE formula using 2 calculations

ADDDATE formula using 2 calculations

Hello, I want to create an ADDDATE formula using 2 calculations,  add 1 month and deduct 1 day.

the formula that I need should look like this:
ADDDATE(due_date, 1, "Months")+
ADDDATE(due_date, -1, "Days")

Each row itself works fine, but when I'm trying to combine them into one formula, it doesn't work. Can anyone look into fixing it?

Thank you