Question

5. Find the sum of the first 40 terms of the series 1 -2 +3 -4 +....

Answer 1

I hope that you would understand the solution.

if you have any other doubts ,don't hesitate to ask.

regards
nimit sharma

Answer 2

Sum of 1 - 2 + 3 - 4 + ... 40 terms

= ( 1 - 2 )+( 3 - 4 )+( 5 - 6 )+ ..20 pairs

= -1 -1 - 1 - 1 .....20 terms

= ( -1 ) × 20

= -20

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