The formula for an arithmetic sequence is An=A1+(n-1)d.
Using this knowledge, you can set up the equation easily to be An=1+(12-1)-5
You then simplify this to 1-55 using PEMDAS, giving you the answer for the twelfth term being -54, you then do this for every term if you want (or you could just subtract 5 by the terms after 14 till you get to -54. After all that, you add the twelve terms up to get -319 as your final answer
Answer:
c b a
Step-by-step explanation:
