The 7th term of an arithmetic sequence is 21, and the tenth term is 126. Find th

vazelinahS 2021-08-17 Answered
The 7th term of an arithmetic sequence is 21, and the tenth term is 126. Find the 1st term?

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Expert Answer

SchepperJ
Answered 2021-08-18 Author has 17891 answers
The answer is -189. The difference between each term is 35 because 126 - 21 = 105. \(\displaystyle\frac{{105}}{{3}}\) (because of the difference between 7 and 10) = 35 and then you would have to \(\displaystyle{35}\times{\left(-{6}\right)}\) to go back to the first term . With that you would get -210 and then you would have to add 21 because of where you started at (7th term).
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