Step by step
The question
Question: is {(4, 2), (4, −2), (9, 3)} a function?
{(4, 2), (4, −2), (9, 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 Each x and its y
4 goes to 2 and −2.
One x, two different y's!
4 → 2, −2
9 goes to 3.
9 → 3
2 Read the answer
4 has two y's.
So it is not a function.
= no, not a function
3 Check
Let's check on a grid.
Draw the grid.
We plot the points.
A straight up-and-down line at x = 4 meets two points.
Two points on one up-and-down line: not a function.
The same answer!
Let's look back.
First: each x and its y.
Then: read the answer.
Last: check.
Answer
= no, not a function