Hey there!
The way that I always solved these problems is just plugging in the values into the given function in the answers. You could also graph these equations, too, and see if the points you've been given are on the graph. I see you're on a Mac, so you should have Grapher on there. Just make sure that if you're using Grapher, you set each equation to y instead of tₓ, since the program won't know what to do with the latter.
For your first problem, whichever function is equal to 17 when you input 1 (since it's the first number in the sequence) for n will be your answer.
5(1) + 16 = 5 + 16 = 21
5(1) + 12 = 5 + 12 = 17
–5(1) + 12 = –5 + 12 = 7
5(1) + 31 = 5 + 31 = 36
Your answer will be B, since it's the only function that contains the point (1, 17).
For your second problem, just do the same thing, except the function that's equal to 1 when you input 1 for n will be your answer this time.
–7(1) = –7
–7(1) – 6 = –7 – 6 = –13
–7(1) + 8 = –7 + 8 = 1
7(1) + 8 = 7 + 8 = 15
Your answer will be C, since the graph of the function contains the point (1, 1).
Hope this helped you out! :-)
