Page 271 - Math Smart - 7

Linear Line Graphs
Given the equation of a linear graph, we work out the values for by substituting fixed values for x.
Example
Apples are sold at $3 per kilogram.
Cost of apples iy) = $3 x mass of apples in kilograms U).
We write the equation of the line as y = 3x
We can work out ordered pairs or coordinates on the graph using a table.
Total cost of apples
Mass (kg) 0 1 2 3 4
Total cost ($) 0 3 6 9 12 20
18 /
/
Plan the scales of the axes to fit all the coordinate 16 /
14
points on the graph paper. /
12
Plot the points on the graph. 10
8
Draw a straight line through the points.
6
4
/
2
0
—<>—
Total cost
Distance-time graphs

The vertical axis represents distance. The horizontal axis represents time.
The blue line shows constant speed. The object is moving away from the starting point at a constant speed.
The red line shows a journey with a stop from the 4*^ to 8'^ second. Then the object slows down.

Different types of movement

100
stf ad) /
90
fastspeed /
80
/
70
/
60
/
>tat oni ry
50 1
/ / \
40
/ / re urn to
30
/ ^St(ad) st< rtin 9
20 ml
10 / spjed C
/
\
0
1 i > i 0
Time (s)