標題:

sequence

發問:

If the first term of an arithmetic sequence is 7 and the sum of the first 10 terms is 325,find the 10th term. 更新: find the sum of the first 10 terms of an arithmetic sequence if its 4th term is 10 and the common difference is 2.

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最佳解答:

1. If the first term of an arithmeticsequence is 7 and the sum of the first 10 terms is 325，find the 10thterm. Sol a1=7 S10=(a1+a10)*10/2 325=(7+a10)*5 a10=58 2. find the sum of the first 10 terms of an arithmetic sequence if its 4th termis 10 and the common difference is 2. Sol a4=a1+3d 10=a1+3*2 a1=4 a10=a1+9d=4+18=22 S10=(a1+a10)*10/2=(4+22)*5=130

其他解答:4E350C6F8B48ECA2
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