Step by step
The question
Question: is x = −2 a function?
x = −2
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 = −2.
Every point has x = −2.
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 = −2 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 (−2, 0), (−2, 1), (−2, 2) are all on it.
One x, many y's.
The same answer!
(−2, 0), (−2, 1), (−2, 2), ... all have x = −2
Let's look back.
First: draw the graph.
Then: vertical line test.
Then: read the answer.
Last: check.
Answer
= no, not a function