Step by step
The question
Question: is x = 3 a function?
x = 3
A function is a rule where each x has only one y.
One x in, one y out.
function: each x has only one y
1 Draw the graph
Draw the grid.
Draw x = 3.
Every point has x = 3.
It is a straight up-and-down line.
2 Vertical line test
The vertical line test: draw straight up-and-down lines.
If one of them hits the graph two times, one x has two y's.
Then it is not a function.
A vertical line at x = 3 lies right on top of the graph.
It hits every point of it!
a vertical line with 2 hits → not a function
3 Read the answer
One vertical line hits it more than once.
So it is not a function.
= no, not a function
4 Check
Let's check with numbers.
The points (3, 0), (3, 1), (3, 2) are all on it.
One x, many y's.
The same answer!
(3, 0), (3, 1), (3, 2), ... all have x = 3
Let's look back.
First: draw the graph.
Then: vertical line test.
Then: read the answer.
Last: check.
Answer
= no, not a function