Straight-line equations (also called "linear equations") can take many forms. One of them is called the "point-slope" form. Suppose you know a point (x1, y1) and a slope m, then the straight line equation will take the following format:

y – y1 = m(x – x1)

For example, suppose we have a straight line that has slope m = 4 and passes through the point (–1, –6). Then the equation for the straight line will be:

y - ( -6 ) = 4 ( x - (-1)), Or

y + 6 = 4 ( x + 1 ), Or

y = 4x - 2