Linear equation

A linear equation is an equation in which each term is either a constant or the product of a constant times the first power of a variable. Such an equation is equivalent to equating a first-degree polynomial to zero. These equations are called "linear" because they represent straight lines in Cartesian coordinates. A common form of a linear equation in the two variables x and y is

In this form, the constant m will determine the slope or gradient of the line; and the constant term b will determine the point at which the line crosses the y-axis. Equations involving terms such as x2, y1/3, and xy are nonlinear.