Step by step
The question
Question: is {(−2, 4), (2, 4), (−2, −4)} a function?
{(−2, 4), (2, 4), (−2, −4)}
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
−2 goes to 4 and −4.
One x, two different y's!
−2 → 4, −4
2 goes to 4.
2 → 4
Careful!
4 comes out twice, from two different x's.
That is fine.
Only one x with two y's breaks the rule.
Careful: the same y twice is fine (4)
2 Read the answer
−2 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 = −2 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