Q. An arithmetic sequence is defined as follows:{a1=−138ai=ai−1+6Find the sum of the first 35 terms in the sequence.
Identify Terms: Identify the first term a1 and the common difference d of the arithmetic sequence. The first term a1 is given as −138, and the common difference d is given as 6.
Find 35th Term: Use the formula for the nth term of an arithmetic sequence, which is an=a1+(n−1)d, to find the 35th term (a35). We have a1=−138, d=6, and n=35. So, a35=−138+(35−1)×6.
Calculate 35th Term: Calculate the 35th term using the values from the previous step. a35=−138+(34×6)=−138+204=66.
Find Sum of 35 Terms: Use the formula for the sum of the first n terms of an arithmetic sequence, which is Sn=2n×(a1+an), to find the sum of the first 35 terms. We have n=35, a1=−138, and a35=66. So, S35=235×(−138+66).
Calculate Sum: Calculate the sum using the values from the previous step. S35=235×(−72)=17.5×(−72)=−1260.
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