Define the function by , . Complete the table given below by using this definition. What is the domain and range of this function? Draw the graph of .
This problem asks you to evaluate the squaring function at integer inputs, then state its domain and range, and sketch its graph. The key idea: squaring always gives a non‑negative output, so the range is . The completed table shows the symmetric pattern of squares, and the graph is the familiar upward‑opening parabola.
Why this approach works
Function evaluation is the simplest operation in algebra: you replace the variable with the given number and compute. For , that means multiplying the input by itself. The table is just a list of these evaluations. Once you see the outputs, the domain (all real numbers) and range (all non‑negative reals) become obvious. The graph is a parabola — symmetric about the -axis because — and its shape is determined by the points you’ve just computed.
1. Fill the table
For each , compute :
- :
- :
- :
- :
- :
- :
- :
- :
- :
The completed table:
Notice the symmetry: . This happens because . So you only need to compute for non‑negative and mirror the results.
2. Domain
The domain is the set of all inputs for which the function is defined. Since works for every real number — you can square any real — the domain is all of .
3. Range
The range is the set of all possible outputs. A square is never negative: for every real . Also, every non‑negative number is the square of some real number (its square root). So the range is all real numbers from upward.
A common mistake is to think the range is because the domain is . But squaring “folds” the number line: both and give , and nothing gives a negative output. Always check the sign behaviour.
4. Graph of
Plot the points from the table: , , , , , , , , .
These points lie on a smooth curve called a parabola. The graph:
- Opens upward (since the coefficient of is positive).
- Has its vertex (lowest point) at .
- Is symmetric about the -axis.
- Gets steeper as increases.
A rough sketch:
y
|
16 - * *
|
9 - * *
|
4 - * *
|
1 - * *
|
0 - *---*---*---*---*---*---*---*---*---> x
-4 -3 -2 -1 0 1 2 3 4
(Imagine a smooth U‑shaped curve passing through all these points.)
The graph of is the prototype parabola. Every quadratic is a transformation of this basic shape.
The completed table shows for to ; the domain is ; the range is ; and the graph is an upward‑opening parabola with vertex at the origin.
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