SOLUTION: I have solved this problem but not sure if my answer is right or wrong want to know from you guys so please help me i have to submit my assignment and tomorrow is the last date PLE

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Question 1022735: I have solved this problem but not sure if my answer is right or wrong want to know from you guys so please help me i have to submit my assignment and tomorrow is the last date PLEASE PLEASE NEED HELP 😢
The 8th term of an arithmetic sequence is 25 and the 20th term is -11.Find the first term of the sequence and the commom difference and use these to write the general term .
According to my answer the general term is tn=49.5+(n-1)(-3.5)
Thanks in advance ☺
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
No with your formula the 8th term is 25 but the 20th term is -17.
a%5B8%5D=a%5B1%5D%2B%288-1%29%2Ad=a%5B1%5D%2B7d=25
a%5B20%5D=a%5B1%5D%2B%2820-1%29%2Ad=a%5B1%5D%2B19d=-11
So then,
a%5B20%5D-a%5B8%5D=-11-25
a%5B1%5D%2B19d-a%5B1%5D-7d=-36
12d=-36
d=-3
and
a%5B1%5D%2B7%28-3%29=25
a%5B1%5D-21=25
a%5B1%5D=46
So then,
a%5Bn%5D=46-3%28n-1%29
a%5Bn%5D=46-3n%2B3
highlight%28a%5Bn%5D=49-3n%29
You can verify that the 8th and 20th term match what you need.