Question

find the sum of the following series upto n terms 1+5+11+19+....​

Answer 1

Hey mate here is your answer

Answer:

1=1

5= 1+4

11=5+6

19 = 11+8

29= 19 + 10

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The add all the equations and cancell the common terms to get

Tn = 1+{4+6+8+10+....to n terms}= 1+2{2+3+4+5+.... n terms} = 1+(n+2)(n-1) = n^2 + n -1

Now the reqd sum = n(n+1)(2n+1)/6 + n(n+1)/2 + n.

I assume that you know the summation formulae. If not revise those first!

I hope it helps you and mark brainliest ✌✌✌✌

Answer 2

Your answer is in the attachment