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 .