# The nth sum of a series is given by the formula Sn = 1 – 4n. how do you workout the first three terms of the sequence?

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Expert Answers

thilina-g | Certified Educator

The sums of a series is given by

`S_n = a_1+a_2+a_3+.....+a_(n-1)+a_n`

Therefore,

`S_1 = a_1`

`1-4xx1 = a_1`

`a_1 = -3`

and,

`S_2 = a_1+a_2`

`1-4xx2=-3+a_2`

`a_2 = 1-8+3 = -4`

and,

`S_3 = a_1+a_2+a_3`

`1-4xx3 = -3-4+a_3`

`a_3 = 1-12+3+4 = -4`

Therefore the first three terms are -3, -4, -4