Step by step
The question
Question: find f(2) for f(x) = 5x − 1.
f(x) = 5x − 1
f(x) is read "f of x".
It is a rule, called a function.
A number goes in for x.
The rule gives one answer out.
f(x) = "f of x"
x goes in → an answer comes out
1 Put the number in
f(2) means: put 2 in place of every x.
We write it in brackets.
f(2) = 5(2) − 1
2 Times and divide
Times comes before minus.
Order: ( ) → x² √ → × ÷ → + −
5(2) = 5 × 2
5(2) means 5 times 2.
5 times 2 is 10.
= 10 − 1
3 Plus and minus
10 minus 1 is 9.
f(2) = 9
So f(2) = 9.
Let's look back.
First: put the number in.
Then: times and divide.
Last: plus and minus.
Answer
f(2) = 9