Point-slope Form of Equations of Straight Lines
How can we find the equation of L? Suppose we are given a point A(x1, y1) on a straight line L with slope m. How can we find the equation of L? Let P(x, y) be a point on L. Slope of AP = slope of L y – y1 i.e. m = x – x1 y – y1 = m(x – x1)
Point-slope Form The equation of L passing through A(x1, y1) with slope m is given by: y – y1 = m(x – x1)
Follow-up question Find the equation of the straight line passing through (–1, 6) with slope –2. The equation of the straight line is y - 6 = -2[x - (-1)] y - 6 = -2x - 2 y = -2x + 4 y – y1 = m(x – x1)