Question

The sum of first 'n' terms of an arithmetic sequence is 2n*+3n algebraic form of the expression​

Answer 1

Answer:

Example 1:

Find the sum of the first 20 terms of the arithmetic series if a1=5 and a20=62 .

S20=20(5 + 62)2S20=670

Example 2:

Find the sum of the first 40 terms of the arithmetic sequence

2,5,8,11,14,⋯

First find the 40 th term:

a40=a1+(n−1)d        =2+39(3)=119

Then find the sum:

Sn=n(a1+an)2S40=40(2 + 119)2=2420

Step-by-step explanation:

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