Derive the graph of linear demand function with explanations.

You are right, Dipen. Lemme help you.

The equation of linear demand function,
Q^d = a - bP

where a and b are parameters and a, b > 0.

a is a finite value which indicates that at price = 0, consumers will buy ‘a’ amount of goods.

-b is the slope of function:

when, Q^d = 0

we get, 0 = a - bP

so, P = $\hat P$ = $\frac ab$

At $\hat P$ = $\frac ab$, the quantity demanded will be 0. The negative is introduced in slope (b) in order to show if the price increases then quantity demand decreases.

A graph is shown below: