Thread: straight-line graph

can anyone tell me when a straight-line graph is used in a real life situation where it may be applicable?

Thanks,

To show whether profit has declines or went up. For example, say I make overall 200 dollars a day but the cost to make this money is 100 dollars. So I have the linear equation y = 200x - 100, in which y is the profit and x is the number of days. Then as time increases (the x - axis), I can show how our profit increases (the y - axis).