<u>Answer:</u>
-348
<u>Step-by-step explanation:</u>
We are given the following arithmetic sequence and we are to find the sum of its first 12 terms:
1, -4, -9, -14, . . .
For that, we will use the formula for the sum of the arithmetic mean:

We know the value of the first term (
) but we need to find the value of
. So we will use the following formula:



Substituting these values in the sum formula to get:

-348
It would be pi over 6, 5 pi over 6, and 3 pi over 6.
From what you said the choices go up by 3 every time in different combinations . Its at least 36 or more combinations .
i did my best guess from the choice .. hope it helps
40/1.4=28.57 i think this is right