MR=△TR/△Q

△TR=TR(after)-TR(before)=(P+△P)(Q+△Q)-PQ=P△Q+Q△P+△P△Q

therefore, MR=△TR/△Q=P+△P+Q△P/△Q.

BUT the actual function of MR is MR=P+Q△P/△Q

Why there is a difference △P between these two functions?

MR=△TR/△Q

△TR=TR(after)-TR(before)=(P+△P)(Q+△Q)-PQ=P△Q+Q△P+△P△Q

therefore, MR=△TR/△Q=P+△P+Q△P/△Q.

BUT the actual function of MR is MR=P+Q△P/△Q

Why there is a difference △P between these two functions?

What you’re calling the *actual* function is an approximation, when ∆P is small enough to ignore.

1 Like

Thank you!

My pleasure.