Numerical: Find the equation of the line through(– 2, 3) with slope – 4. Solution: Here Slope m = – 4 and given point( x0, y0) is(– 2, 3). Using slope-intercept form formula, y – y0 = m( x – x0), we get y – 3 = – 4( x + 2) or 4x + y + 5 = 0
Two point form
If two fixed points P1( x1, y1) and P2( x2, y2) of a line is known, then we can write the equation of the line. Let P( x, y) be a general point on L. The three points P1, P2and P are collinear, therefore, we have slope of P1P = slope of
P1P2.