Take a look at the applet: Linear Function
If is a linear function of then the corresponding formula can be written as , where
is the gradient, that is the increase (decrease) of per unit step ;
is the y-intercept, the value of the function if .
The graph of such a linear relationship is a straight line through .
If you then increase the value of by , the function value will increase (or decrease) by .
The gradient is also called the slope, because this number determines the direction of the line.