A linear equation is an algebraic equation in which each term is either a constant or the product of a constant and (the first power of) a single variable.

Forms for 2D linear equations

Slope�intercept form

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where m is the slope of the line and b is the y-intercept, which is the y-coordinate of the point where the line crosses the y axis. This can be seen by letting x = 0, which immediately gives y = b. Vertical lines, having undefined slope, cannot be represented by this form. (Our solved example in mathguru.com uses this concept)

http://en.wikipedia.org/wiki/Linear_equation#Point.E2.80.93slope_form

The slope of a line in the plane is defined as the rise over the run, m = Δy/Δx.

In mathematics, the slope or gradient of a line describes its steepness, incline, or grade. A higher slope value indicates a steeper incline.

The slope is (in the simplest of terms) the measurement of a line, and is defined as the ratio of the "rise" divided by the "run" between two points on a line, or in other words, the ratio of the altitude change to the horizontal distance between any two points on the line. Given two points (x₁,y₁) and (x₂,y₂) on a line, the slope m of the line is

http://en.wikipedia.org/wiki/Slope

The above explanation is copied from Wikipedia, the free encyclopedia and is remixed as allowed under the Creative Commons Attribution- ShareAlike 3.0 Unported License.