Step by step
The question
Question: find g(−3) for g(t) = 5 − 2t.
g(t) = 5 − 2t
g(t) is read "g of t".
It is a rule, called a function.
A number goes in for t.
The rule gives one answer out.
g(t) = "g of t"
t goes in → an answer comes out
1 Put the number in
g(−3) means: put −3 in place of every t.
We write it in brackets.
The brackets keep the minus with the number.
g(−3) = 5 − 2(−3)
2 Times and divide
Times comes before minus.
Order: ( ) → x² √ → × ÷ → + −
2(−3) = 2 × (−3)
+ × − = −
2(−3) means 2 times −3.
Plus times minus is minus.
2 times 3 is 6.
So we get −6.
= 5 − (−6)
3 Plus and minus
Taking away a negative is the same as adding.
− (−) = +
So 5 − (−6) becomes 5 + 6.
= 5 + 6
5 plus 6 is 11.
g(−3) = 11
Careful!
Many people go from left to right and get −9.
But times and divide come before plus and minus.
Careful: not 5 − 2(−3) = −9 ✗
So g(−3) = 11.
Let's look back.
First: put the number in.
Then: times and divide.
Last: plus and minus.
Answer
g(−3) = 11