Slope of the budget line

x2 = m/p2 + p1x1/p2.

This is the formula for a straightline with a vertical intercept of m/p2 and a slope of p1/p2.

The slope of the budget line has a nice economic interpretation.It measures therate at which the market is willing to “substitute” good1 for good2.

Economists sometimes say that the slope of the budgetline measures the opportunity cost of consuming good1.In order to consume more of good1 you have to give up some consumption of good2.Giving up the opportunity to consume good2 is the true economic cost of more good1 consumption; and that cost is measured by the slope of the budget line.

For mathematical equation refer the video.