Question

find sigma r=1 upto n (1+2+3....+r upon r)​

Answer 1

Step-by-step explanation:

1+2+3+4....+r

sum of consecutive numbers formula = x(x+1)/2 where 'x' is the last term.

In this case 'x' = r

So r(r+1)/2/r = r(r+1)/2r

Now, take r = 1

(1x2)/2 = 1

r=2

2(3)/4 = 3/2

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r=n

n(n+1)/2n

Hope it helps:)