Drawing-Graphs-From-Tables Wjec-Eduqas Foundation

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Exam code:C300

Drawing graphs using a table

To create a table of values
- substitute different x-values into the equation
- This gives the y-values
To plot the points
- Use the x and y-values to mark crosses on the grid at the coordinates (x , y )
- Each point is expected to be plotted to an accuracy within half of the smallest square on the grid
Draw a single smooth freehand curve
- Go through all the plotted points
- Make it the shape you would expect
  - For example, quadratic curves have a vertical line of symmetry
- Do not use a ruler for curves!

For quadratic graphs, be careful substituting in negative numbers
Always put brackets around them and use BIDMAS
- For example, x = -3 in y = –x² + 8x
  - becomes y = -(-3)² + 8(-3)
  - which simplifies to -9 – 24
  - so y = – 33
For reciprocal graphs like $y equals 1 over x$ , do not include x = 0
- You cannot divide by zero
  - You get an error on your calculator
- There is no value at x = 0
  - The L-shaped branches can’t cross the y-axis
- An example is given below with $y equals 1 over x$

<td class=”border border-dark ContentBlock_tableCell__N2pb_” colspan=”1″

$x$	-3	-2	-1	0	1	2	3
$y$	$negative 1 third$	$negative 1 half$	$negative 1$