Domain — Grade 8 Math, what it means and where it is taught
The set of allowed inputs.
Taught in Grade 8 Math.
Where it is taught
What uses it later
This idea is needed for:
- Excluded value — An input that makes the denominator zero. It can never be in the domain.
Practise this idea
3 questions in the course bank use Domain, in What Is a Function?, Sequences, Explicit & Recursive.
Problem 1
For f(x) = 1x - 4, which value must be excluded from the domain?
Worked answer
4
x - 4 = 0 when x = 4
That input has no output
Exclude x = 4
Problem 2
For f(x) = x2 with domain {-2, -1, 0, 1, 2}, list the range.
Worked answer
{0, 1, 4}
4, 1, 0, 1, 4
Distinct values: 0, 1, 4
Problem 3
The graph of a sequence is
- a set of separate points
- a continuous line
- a smooth curve
- a shaded region
Worked answer
a set of separate points
Only the counting numbers
So the graph is separate dots
Never join them