# Which Is The Better Way To Calculate Marginal Revenue? Using Derivative Or R(Q)-R(Q-1)?

I Still A Bit Confused About Marginal Revenue. Since Marginal Revenue Is The Additional Revenue We Get From Producing 1 Additional Good. That Means Marginal Revenue Is R(Q) - R(Q-1). My Teacher Says That We Can Also Get Marginal Revenue Formula From Deriving The Total Revenue Formula, My Book Also Says What My Teacher Said. The Problem Is, I'll Getting Different Marginal Revenue Formula From That 2 Ways.

Example For P = 6 - Q TR = 6Q - Q^2 If We Used R(Q)-R(Q-1) We Will Get : 7-2Q If We Used The Derivative Of Total Revenue It Will Be : 6-2Q

The R(Q)-(Q-1) Formula Is More Accurate (At Least For This Case) Which Formula Should I Use?