OCR Advanced FSMQ - Additional Maths

y x 0 2 y x 0 5 Equation is y = 5 Equation is x = 2 y x 0 –4 y x 0 –3 Equation is x = −4 Equation is y = −3 6.8 Finding the equation of a straight line To find the equation of a straight line you need to know the gradient of the line ( m ) and the coordinates of a point ( x 1 , y 1 ) that lies on the line. The equation of a straight line with gradient m and which passes through a point ( x 1 , y 1 ) is given by: For example, the equation of the straight line with a gradient of 2 and passing through the point (2, 5) is y − 5 = 2( x − 2) y − 5 = 2 x − 4 So y = 2 x + 1 or 2 x − y + 1 = 0 y − y 1 = m ( x − x 1 ) Note that here x 1 = 2, y 1 = 5 and m = 2 in the equation y − y 1 = m ( x − x 1 ) A line parallel to the x -axis will always have the equation y = a number and a line parallel to the y -axis will always have the equation x = a number. 6 Coordinate geometry of straight lines 129