How do I know if the function is a linear function?

This is not a linear function.

Step-by-step explanation:

It is a quadratic function.  If you were to make a table of the x and y values of the function it would look like this:

x    y

0   -4

1   -1

2    8

Just by looking at these three values, we can see that they do not increase at a consistent rate.  It increases by 3 from 0 to 1, but increase by 9 from 1 to 2.  You can tell if a function is linear by seeing if it increases at a constant rate.  (In this case it does not)

c

step-by-step explanation:

c

question 1 is 8, question 2 is 9, question 3 is 24

step-by-step explanation:

now, the numbers they give you at the top are the key. from there, you just have to plug and chug! let's try 1, 2, and 3!

key: a=3, b=5, c=6

1. a+5

remember, a=3, so we plug that in to get 3+5=8

2. 15-c

c=6, so we plug that in to get 15-6=9

3. 4b

b=6, so we plug it in to get 4*6=24

time to try the rest on your own! if you put the answers below in a comment, i'll check them for you!