Question

1,2×3,3×9,4×27,5×81,........ find Sn of the following arithmetic -geo

a=1
d=1
r=3

sn=a/1-r+dr[(1-rn-1)]/(1_r)^
=1/1-3+1×3(1-3n-1)/(1-3)^
=-1/2+(3-3n)/(2)^
=-1/2+(3-3n)/4​

Answer 1

Answer:

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