What is the calculation formula of monthly mortgage payment? How to calculate monthly mortgage repayment

There are two payment methods for mortgage: equal principal and interest and average principal. The specific formula is as follows: equal principal and interest: [loan principal × monthly interest rate× (1+monthly interest rate) repayment months ]=[( 1+ monthly interest rate) repayment months-1] average principal: monthly repayment amount = (loan. Two months is quadratic.