A linear equation is an algebraic equation of the form y = m x + b involving only a constant and a first-order (linear) term, where m is the slope and b is the y-intercept. The above form is aptly known as slope-intercept form; alternatively, linear equations can be written in a number of other forms including standard form, intercept form, etc. Occasionally, the above is called a "linear equation of two variables, " where y and x are the variables. Equations such as x = 3 and y = 2 are linear equations of a single variable, and 2x + 4y + 5z - 6 = 0 is an example of a linear equation with three variables.