Worked example 1 A function is defi ned as f (x) = 3x − 4 Find: (i)
f (5) (ii) Solution f ( 5 ) is pronounced ‘ f of 5 ’ (ii)
f (x) = 8 is pronounced ‘ f of x is equal to 8′
f (−1) (iii)
f (x) = 8
(iv)
f (x) = 20
Graphing a linear function 1
Input (x value)
2 3
Find two points that satisfy the equation by creating a table. Choose any two values for x and fi nd the corresponding y value. It is better to choose small whole numbers as they are easy to graph on the Cartesian plane.
Function Output ( y value)
Plot the points on the Cartesian plane. Draw a straight line through both points.
Worked example 2 Graph the function f (x) = 2 + 3x
Solution (1, 5) Point ( x value, y value)
You need only two points to graph a linear function. Why is this?