Demand Function, Demand Schedule and Demand Curve

Demand function expresses quantity demanded as depending on price and the other determinants, written generally as:

where $Q_d$ is quantity demanded of good $x$, $P_x$ its own price, $P_r$ the price of related goods, $Y$ income, $T$ tastes and $E$ price expectations. For the Law of Demand, this is simplified to $Q_d = f(P_x)$, other variables held constant.

A simple linear demand function used throughout Gujarat Std 11 Economics numericals takes the form $Q_d = a - bP$, where $a$ and $b$ are positive constants ($a$ is the quantity demanded when price is zero, and $b$ shows how much quantity falls for every one-unit rise in price).

Demand schedule is a tabular statement showing the different quantities demanded of a good at different prices, at a given time, other things constant. For example: