Find the sum of the first 12 terms of the sequence. if the answer is negative, do not enter any spaces in between the number and the negative sign. 1, -4, -9, -14, . .

Explanation:

The formula to use is

S = (n/2)*(2*a1+d*(n-1))

where

S = sum of the first n terms = unknown

n = number of terms = 12

d = common difference = -5

a1 = first term = 1

So we get the following

S = (n/2)*(2*a1+d(n-1))

S = (12/2)*(2*1 + (-5)*(12-1))

S = 6*(2 - 5(11))

S = 6*(2 - 55)

S = 6*(-53)

S = -318

step-by-step explanation:

ok so im not 100% sure but you would start by adding 5.1t and 1.9t beacuse they have the same variable. that is 7t.   then add -3.6 + 1.2 which is -2.4

so then keep that as -2.4 + 7t. i apologize if this is incorrect. best luck on your test < 3