Equation of Straight Line Equation of a straight line (gradient-intercept form): y = mx + c where m is the gradient and c is the y-intercept. Equation of a straight line (given gradient and 1 point):
Finding equations Find the equation of the straight line joining (2, 4) and (–2, 3) (–2, – 4) and (1, –7)
Finding equations Find the equation of the lines, given the gradient and the coordinate of a point lying on the line. (a) m = 3, (1, 1) (b) m = 0.5, (5, 7)
Finding Equations • What is the equation of the line which has gradient 2 and which passes through the origin?
Finding Equations • Find the equation of the straight line that is parallel to and bisects the line segment joining the points (3, 1) and (1, –5).
Finding Equations Find the values of k if the line is parallel to
Finding Equations Given the line, find • its gradient; • the coordinates of the point at which it cuts the x-axis.
Double-intercept form General form Gradient-intercept form *Given gradient and 1 point Straight line equations of different forms
Collinear Points 3 points are collinear if gradient AB = gradient BC