<Dl> <Dd> y = b (\ displaystyle y = b \,) Horizontal Line y = b </Dd> </Dl> <Dd> y = b (\ displaystyle y = b \,) Horizontal Line y = b </Dd> <P> This is a special case of the standard form where A = 0 and B = 1, or of the slope - intercept form where the slope m = 0 . The graph is a horizontal line with y - intercept equal to b . There is no x-intercept, unless b = 0, in which case the graph of the line is the x-axis, and so every real number is an x-intercept . </P> <Dl> <Dd> x = a (\ displaystyle x = a \,) Vertical Line x = a </Dd> </Dl>

Definition of a linear equation in two variables