In my Managerial Econ book, by Allen, Weigelt, Doherty & Mansfield (8th Ed., 2012) on pgs 41-42, in Chapter 2, Demand Theory, there is a section titled "The Effect of Price Elasticity on the Firm's Revenue"

In this section, the following paragraph is the context for my question:

"If the demand for the product at a given price is price inelastic, the price elasticity of demand is greater than -1. Following from our definition of inelastic demand, the percentage change in quantity is less than the percentage change in price. Hence if we increase price, total revenue will increase because the slightly higher price per unit sold will more than offset the decrease in units sold. If demand is inelastic and we decrease price, total revenue will decrease because the increase in units sold cannot offset the lower price per unit sold. We can easily show this relationship formally.

Let TR = P x Q (total revenue = price per unit * number of units sold)

(1) TR/P = Q (P/P) + P (Q/P)

(2) Q(P/P) + Q(P/Q)(Q/P) = Q(1 + )

Also we are given earlier on, the following: "The price elasticity of demand is defined as the percentage change in quantity demanded resulting from a 1% change in price. More precisely it equals

= (P/Q) Q/P

My questions:

a) How did they get (1) from TR = P x Q?

b) Is the price elasticity of demand?

~ If you need more context, please let me know. Thanks!