Linear Inequalities in Two Variables
Number line
A line on which numbers are marked at equal intervals, used to show the solution of an inequality.
| English | Number line |
|---|---|
| Bahasa Melayu | Garis nombor |
| 中文 | 数轴 |
How it is used
The solution x ≥ −2 is drawn on a number line by placing a closed circle at −2 and shading the arrow to the right, so −2, 0, 3 and every larger value are included.
Where it shows up in SPM
Used to represent the solution of a one-variable linear inequality in Form 4. Paper 1 objective questions often show a number line and ask which inequality it represents, or the reverse.
It is the one-dimensional counterpart of shading a region in two variables.
Don't confuse it with
Open the chapter: Linear Inequalities in Two Variables →
Frequently asked questions
What does an open circle versus a filled circle mean on a number line?
A filled (closed) circle means the value is included, matching ≤ or ≥. An open circle means the value is not included, matching < or >.
For x > 3 use an open circle at 3; for x ≥ 3 fill it in.
Which way does the arrow point?
Shade toward larger numbers (right) for x > a or x ≥ a, and toward smaller numbers (left) for x < a or x ≤ a. Reading the direction directly from the sign after x avoids mistakes; x ≤ 1 shades left from a filled circle at 1.