- Education and Science
Straight line graphs. How to plot a sloping line in math using a table of values.
The easiest way to plot a line graph (a sloping line) is to use a table of values, which can also be called a coordinate table. All you need to do is to pick some x coordinates (at least 3, as 2 is not a good idea!), and use your formula to work out the y coordinates. Then plot your points on your coordinate grid, and draw your line through the coordinate points.
Plot the graph of y=2x
The x coordinates that I’m going to pick are 0, 1 and 2. But, you might want to choose different values.
X 0 1 2
Y ? ? ?
To work out the y coordinates in our table of values, you need to substitute these values into your formula y=2x. Do this by multiplying your x coordinates by 2.
X 0 1 2
Y 0 2 4
So our coordinates that our line passes through are (0,0), (1,2) and (2,4).
Plot these onto our coordinate grid, and draw your line through the points. Make sure the line extends all the way across the coordinate grid.
Plot the graph of y = -3x +8
Again, choose 0, 1 and 2 as your x coordinates.
This time we need to times the x coordinates by -3, and add on 8 to find the y coordinates. So our table of values will look like this:
X 0 1 2
Y 8 5 2
So our straight line passes through the points (0,8), (1,5) and (2,2).
Now plot these onto your coordinate grid, and draw your straight line through these points.
Check out these hubs for more help on plotting graphs: