Straight Line Graphs

Straight Line Graphs

1. Equation for a straight line shows relationship between X and Y coordinates

   • To work out whether a pair of coordinates is on a line or not
     • Take an X coordinate and substitute it into the equation
       • Example: y=2x-1 x=5 y=9 this is on the line
         • Whereas the coordinates (3,2) would not be on the line

2. Drawing a straight line from the equation

   • Pick 0 as one of your points as the line is then easier to work out
     • work out four points using the equation to create the straight line

3. For large equations such as 5x+3y=15

   • to get a pair of coordinates substitute x as 0 to workout and Y and vice versa

4. What we learn from an equation

   • Y=mx+C
     • M tells us the steepness/gradient of the line
       • The larger the number the steeper the line is
       • If the number is positive the line slopes up and if it is negative it slopes downwards
     • +C indicates where the line crosses the Y axis

5. Working out the equation of a line

   • Workout the Gradient of the line
     • Draw a right angled triangle on the line and use this formula
       • Change in Y/ Change in X
     • Then workout the Y intercept
       • You then add the gradient and the y intercept to the equation y=x