when is budget line called price line - Economics - Theory of Consumer Behaviour

Question

when is budget line called price line?

Ayan Shukla · Accepted Answer

A budget line is called a price line too This is because the
slope of Budget Line is the ratio of prices of goods taken on each
axis in 2-D diagram Algebraically, equation of a budget line is
:
px + qy = M,
where p is the price foe good x and q is the price for good y
Its an equation of a straight line which can alternatively be
written as :
y = (1/q)(M-px)
slope = dy/dx= -(p/q),which is the ratio of price of good x to
price of good y
Also,as price of any of the two goods changes,the budget line
changes its slope or position If both prices increase,the budget
line shifts down and if the both price decreases,budget line shifts
out
Since prices play a great role defining the budget line,it is
also called price line