Question

Find the sum of n terms of the series (4+1n)+(4 - 2n)+(4 - 3n)+.........

Answer 1

(4-n) + (4-2n) + (4-3n) ......... Upto n terms

Separate out all 4s

(4+4 ..... n times) - (n+2n+3n+4n......upto n terms)

4n - n(1+2+3+4......n)

4n - n(n)(n+1)/2

(8n - n^3 - n^2)/2

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