Has anybody seen anything this expression before?

Question

Suppose that $z(cdot)$ is the demand function of an individual (consumer/investor) and $p$ is the price of the commodity/asset demanded. Does anybody know what is the intuition behind the following expression?
begin{align}pz^{'}(p)+z(p)end{align}
It seems to me like the derivative of $(pz(p))^{'}$ with respect to $p$. What is the intuition behind this? Has anybody seen anything this expression before?

Herr K. · Accepted Answer

$pcdot z(p)$ is total revenue (price times quantity), and so its derivative $frac{mathrm d}{mathrm dp}pz(p)=pz'(p)+z(p)$ is marginal revenue.

Dek · Answer

You're correct. Many useful things can be shown by taking this derivative.
Perhaps you were confused because you are used to solving for quantity rather than price - in which case you are more likely to take the derivative of R = z * p(z) with respect to z which gives you p(z) + z * dp(z)/dz

Has anybody seen anything this expression before?

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