Math, asked by ali1234aqduc, 8 months ago

For an A.P if a=1 d=4 what is the value of n if tn=81.

Answers

Answered by sureshchorge78

4

Step-by-step explanation:

a=t1=1

d=4

tn=a+(n-1)d

81=1+(n-1)4

81=1+4n-4

81=-3 + 4n

81+3 =4n

84=4n

84/4=n

21=n

n=21

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