text: A linear equation is an equation involving only the sum of constants or products of constants and 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 two variables is \ny = mx + c \n(e.g. y = 3x + 5)\nIn this form, the value m will determine the slope or gradient of the line; and the value c will determine the point at which the line crosses the y-axis. Equations involving terms such as x2, y1/3, and xy are "non-linear".