HELP ASAPPP!!!

Question

HELP ASAPPP!!!

3mar · Answer

Welcome back!

iwanttogotostanford · Answer

thank you!!!

iwanttogotostanford · Answer

so i have attached the question above

3mar · Answer

Ok I saw it

3mar · Answer

What you picked?

iwanttogotostanford · Answer

can anyone help me solve this?

davejavous · Answer

The general term for the nth term of an arithmetic progression is:
$$a_n = a+(n-1)d$$

You should be able to narrow down your choices already. Look at what information you get get from knowing a_16 and a_17 to put more numbers into the formula above.

iwanttogotostanford · Answer

I think its C but I also believe Im wrong... do you know?

iwanttogotostanford · Answer

@3mar

iwanttogotostanford · Answer

hello?

3mar · Answer

Yes

iwanttogotostanford · Answer

what do you think it should be?

davejavous · Answer

what is the common difference (d) between the terms a_16 and a_17? What do you have to do to go from one to the next?

iwanttogotostanford · Answer

@3mar can you help? do you know the answer or no?

3mar · Answer

I think it is D
Try it to be sure
I am sure

3mar · Answer

What did you subtract or add to get a17 from a16?

iwanttogotostanford · Answer

I did what I was supposed to do and I need to be 100% sure if it is D or not... can you work through it maybe to sho me/ help?

3mar · Answer

Yes of course

3mar · Answer

a16=21
a17=-1
what is the difference?

davejavous · Answer

You should be able to eliminate two incorrect answers immediately by looking at the possible answers and the equation: $$a_n=a+(n−1)d$$
The second stage is to work out the common difference:
$$a_{16} - a_{17} =\; ?$$
What is the common difference?

3mar · Answer

$$a_{17}-a_{16}=22$$
and
n stands for the nth order of the number in the sequence

So D satisfies for a16 and a17

3mar · Answer

Thank you for the medal!

3mar · Answer

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