Step by step
The question
Question: find g(3) for g(x) = x² − x − 6.
g(x) = x2 − x − 6
g(x) is read "g of x".
It is a rule, called a function.
A number goes in for x.
The rule gives one answer out.
g(x) = "g of x"
x goes in → an answer comes out
1 Put the number in
g(3) means: put 3 in place of every x.
Every x becomes 3.
g(3) = 32 − 3 − 6
2 Powers
Powers come before minus.
Order: ( ) → x² √ → × ÷ → + −
3² means 3 times 3.
32 = 3 × 3 = 9
That is 9.
= 9 − 3 − 6
3 Plus and minus
Plus and minus: we go from left to right.
same kind: left → right
9 minus 3 is 6.
= 6 − 6
6 minus 6 is 0.
g(3) = 0
So g(3) = 0.
Let's look back.
First: put the number in.
Then: powers.
Last: plus and minus.
Answer
g(3) = 0