Question

find the sum 1+3+6+..…... to 40 terms​

Answer 1

Answer:

a=1

d=3

an=40

sn=n/2[2a+(n-1) d]

s40=20[2+(39) 3]

s40= 2380

thnx mark brainlist

if this answer is wrong ur question is wrong because 3-1=2

and 6-3=3 common difference is not correct

Answer 2

Step-by-step explanation:

sum to n terms= n/2(first term +last term)

sum to 40 terms= 40/2(1+40)

=>20×41

=>820

YOUR ANSWER IS 820

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