You need to know the y-intercept to write down the equation of a line. In a linear cost function, the slope gives the cost of the first item. If displacement is a linear function of time, then the slope of the graph represents the velocity. If y is a linar function of x, then y increases by a fixed amount for each increase of one unit in y. 14. A real valued function of a real variable is a rule that assigns a number to each specified number in a specified domain.
Some functions assign two or more values to certain numbers in their domains.
The regression line associated with a collection of more than two data points may pass through none of those points.