Respuesta :

Answer:

51

Step-by-step explanation:

when n=1

t 1=1

when n=2

t2=4

as first term is 1 and second term is 4 so the common difference is 3 ,for 6 term if you put this in formula for sum to the n term you will get 51

t1 =1

d=3

n=6

than S6=51

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