Question

If the sum of first 'm' terms of an AP is 3m² – m and its common difference is 6, then find its first term
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Answer 1

Answer:

let sum of first 'm' terms of an ap with first term = a and common difference = 6

since,

Sm = 3m^2-m

d = 6

Sm=m/2 [2a+(m-1)d]

3m^2-m =m/2 [2a +(m-1)6]

3m^2-m =m/2 [2a+(m-1)6]

3m^2-m = m [a+3m-3]

3m-m = [a+3m-3]

2m = [a+3m-3]

2m-3m+3 = a

-1+3 = a

a = 2

Hope its helps you

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