Drawing Straight Line Graphs (OCR GCSE Maths) : Revision Note

Drawing Linear Graphs

How do I draw a straight line from a table of values?

• You may be given a table of values with no equation

• Use the x  and y  values to form a point with coordinates (x , y )

  • Then plot these points

  • Use a ruler to draw a straight line through them 

    • All points should lie on the line

• For example 

  • The points below are (-3, 0),  (-2, 2), ... etc

How do I draw a straight line using y  = mx  + c?

• Use the equation to create your own table of values

  • Choose points that are spread out across the axes given

• For example, plot y  = 2x  + 1 on axes from x  = 0 to x  = 10

  • Substitute in x  = 0, x  = 5 and x  = 10 to get y  coordinates

    • Then plot those points

How do I draw a straight line without using a table of values?

• Start at the y-intercept, c

• Then, for every 1 unit to the right, go up m  units

  • m  is the gradient

  • If m  is negative, go down

  • If m is a fraction, remember that gradient is change in y divided by change in x

    • A gradient of would be units up for every units right

• This creates a sequence of points which you can then join up

  • Be careful of counting squares if axes have different scales

    • 1 unit might not be 1 square