GCSE Maths Notes: Sketching a Quadratic Graph
To sketch a graph we need to
find a set of points. This is most easily done by drawing up a table.
The table for the graph given by the equation
|
|
-3 |
-2 |
-1 |
0 |
1 |
2 |
3 |
|
|
9 |
4 |
1 |
0 |
1 |
4 |
9 |
|
|
3 |
2 |
1 |
0 |
-1 |
-2 |
-3 |
|
+1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
|
|
13 |
7 |
3 |
1 |
1 |
3 |
7 |
When filling in the table
the most important thing to remember is that when you square a minus
number you obtain a positive number, eg
not
-9.
DO NOT RELY ON YOUR CALCULATOR TO WORK OUT THE SQUARE OF A MINUS NUMBER.
Your calculator will tell
you that
which
is exactly wrong:is
correct. The graph is shown below.
