Step by step
The question
Question: find f(−1) on this graph of f.
f(−1) = ?
1 Look at the graph
The graph shows f.
x goes across.
The height of the graph is f(x): we read it on the y axis.
x: across
f(x): the height, up
2 Read f(−1)
The number in the brackets is the x.
Here x is −1.
f(−1): x = −1 → f(x) = ?
Careful!
f of −1 does not mean a height of −1.
The −1 in the brackets is an x.
So we start at −1 on the x axis.
Careful: f(−1): start at x = −1, not at a height of −1
So f(−1) = 1.
f(−1) = 1
3 Check
Let's check.
The answer gives a point.
(−1, 1) means left 1, then up 1.
It lands on the graph.
So the answer is right!
(−1, 1): left 1, up 1 → on the graph
Let's look back.
First: look at the graph.
Then: read f(−1).
Last: check.
Answer
f(−1) = 1