Step by step
The question
Question: find g(−2) for g(t) = 4t + 9.
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.
There are four choices.
First we solve it, the normal way.
Then we pick.
1 Put the number in
g(−2) means: put −2 in place of every t.
We write it in brackets.
The brackets keep the minus with the number.
2 Times and divide
Everyone uses the same order, so we all get the same answer.
Times comes before plus.
4(−2) means 4 times −2.
4 has no sign, so it is plus.
Plus times minus is minus.
4 times 2 is 8.
So we get −8.
3 Plus and minus
Start at −8.
Go right 9.
We land on 1.
So g(−2) = 1.
4 Pick the choice
Our answer is g(−2) = 1.
That is choice B.
5 Why not the others
A is −17.
Wrong: took 9 away instead of adding it.
C is 11.
Wrong: 4 − 2 + 9: added −2 instead of multiplying.
D is 17.
Wrong: 8 + 9: lost the minus sign of −8.
Let's look back.
First: put the number in.
Then: times and divide.
Then: plus and minus.
Then: pick the choice.
Last: why not the others.