Reading a straight-line graph
Read the labelled scales and trace to the requested line. A rule is not needed when the graph shows the values clearly. Write the horizontal value x first and the vertical value y second
- Given a horizontal value Move vertically to the line, then horizontally to the vertical scale
- Given a vertical value Move horizontally to the line, then vertically to the horizontal scale
- Scaled axes Use the value of an interval rather than treating every interval as one
- Axis crossings At the horizontal-axis crossing the vertical coordinate is zero. At the vertical-axis crossing the horizontal coordinate is zero \(\displaystyle \begin{gathered}(x,0)\\(0,y)\end{gathered}\)
Worked example
The graph shows line M
The graph uses unit gridlines
Complete the missing coordinates on line M
| Point | Given form |
|---|---|
| 1 | \((0, ?)\) |
| 2 | \((?, -2)\) |
Start at \(x=0\), move vertically to line M, then read the vertical value
\[(0, -3)\]Start at \(y=-2\), move horizontally to line M, then read the horizontal value
\[(-1, -2)\]
Common mistakes
Difficulty levels
Questions about this topic
Which coordinate comes first?+
Write the horizontal coordinate first, then the vertical coordinate
What if the two axes use different scales?+
Read each axis separately. A horizontal interval and a vertical interval need not represent the same amount
Do I need to find a rule first?+
No. Trace directly to the named line and read the other coordinate from the scale
Can I use a calculator?+
No. This topic is practised without a calculator
Which year level and chapter is this?+
Year 11, VCE Units 1 & 2, General Mathematics, chapter 5: Linear functions and models