Step by step
The question
Question: for which x is f(x) = 3 in this table of f?
f(x) = 3 x = ?
1 Look at the table
The table shows f.
Each x on top has its f(x) right under it.
For example, f of 0 is 3.
x: top row
f(x): right under its x
2 Find where f(x) = 3
This time we know f(x): it is 3.
We look for the x.
f(x) = 3 → 3 in the f(x) row → x = ?
Careful!
Do not stop at the first x.
The table can have the same f(x) more than once.
Careful: look for every x: f(x) can be 3 more than once
Find 3 in the f(x) row.
Right above it: x = 0.
3 is in the f(x) row again.
Right above it: x = 4.
3 is in the f(x) row one more time.
Right above it: x = 8.
So x = 0, x = 4 or x = 8.
x = 0 or x = 4 or x = 8
3 Check
Let's check: put the x back.
Under x = 0 the table has 3.
column: x = 0, f(x) = 3
And under x = 4 the table has 3.
column: x = 4, f(x) = 3
And under x = 8 the table has 3.
So the answer is right!
column: x = 8, f(x) = 3
Let's look back.
First: look at the table.
Then: find where f(x) = 3.
Last: check.
Answer
x = 0 or x = 4 or x = 8