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 |
|
|
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.
