J17

x -5 -4 -3 -2 -1 0 1 2 3 4 5
y -25 -16 -9 -4 -1 0 -1 -4 -9 -16 -25
Note:
(a) The maximum value of the curve is 0 at the origin.
(b) The curve is symmetrical about the y-axis.
Example
Draw the graph of y = x 2 – 3x + 2, for values of x between -1 and +4.
Solution
Make a table of values of x and y:
x -1 0 1 1.5 2 3 4
x 2 1 0 1 2.25 4 9 16
-3x 3 0 -3 -4.5 -6 -9 -12
+2 +2 +2 +2 +2 +2 +2 +2
y 6 2 0 -0.25 0 2 6
Since both x = 1 and x = 2 give y = 0, it is advisable to take a value of x between 1 and
2, i.e. 1.5.
Note that the maximum value of the function is -0.25.