Relationship of the form

*y*=*kx*+*b*where*k*≠ 0 and*b*≠ 0.### Example

The cost of a taxi ride includes a base cost plus another cost related to the distance travelled by the taxi.

If the base cost *b* is $8 and if the cost *x* per kilometre travelled is $1.50, the following relationship determines the total cost *y* : *y* = 1.50*x* + 6.