Step by step
The question
Question: find f(−2) for f(x) = 6 − x².
f(x) = 6 − x2
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.
The brackets keep the minus with the number.
f(−2) = 6 − (−2)2
2 Powers
Powers come before minus.
Order: ( ) → x² √ → × ÷ → + −
(−2)² means −2 times −2.
Minus times minus is plus.
(−2)2 = (−2) × (−2) = 4
That is 4.
= 6 − 4
3 Plus and minus
6 minus 4 is 2.
f(−2) = 2
So f(−2) = 2.
Let's look back.
First: put the number in.
Then: powers.
Last: plus and minus.
Answer
f(−2) = 2