The following sum is a partial sum of an arithmetic sequence

The following sum is a partial sum of an arithmetic sequence; use either formula for finding partial sums of arithmetic sequences to determine its value. sigma^73_i = 6 (2i - 3)

Solution

the sum of arithmetic sequnce is given by

an = a1 + (n-1)d

where

a1 = first term

d = common difference

lets find the 1st term of the sequnce

2(6) - 3 = 9

2nd term

2(7) - 3 = 11

d = 11 - 9 = 2

plugging the values in the formula now

a73 = 9 + ( 73-1)2

a 73 = 9 + (72*2)

sum = 153