Step by step
The question
Question: is {(5, 1), (3, 2), (1, 3), (−1, 4), (−3, 5)} a function?
{(5, 1), (3, 2), (1, 3), (−1, 4), (−3, 5)}
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
We take each x and see where it goes.
5 goes to 1.
5 → 1
3 goes to 2.
3 → 2
1 goes to 3.
1 → 3
−1 goes to 4.
−1 → 4
−3 goes to 5.
−3 → 5
2 Read the answer
Every x has only one y.
So yes, it is a function.
= yes, a function
3 Check
Let's check on a grid.
Draw the grid.
We plot the points.
A straight up-and-down line meets at most one point.
Here at x = 5: one point.
No up-and-down line meets two points.
It is a function.
The same answer!
Let's look back.
First: each x and its y.
Then: read the answer.
Last: check.
Answer
= yes, a function