Answer:
d=-4 and a=10
Step-by-step explanation:
The sum of a arithmetic sequence is given by (n/2)*(2a+(n-1)d). Comparing coefficients with the given Sn, we have; a-d/2=12 and d/2=-2, d=-4 and a=10.
To find the area<span> of a regular </span>polygon<span>, you use an apothem, which is a segment that joins the </span>polygon's center to the midpoint of any side and that is perpendicular (<span> angle of 90°) </span>to that side
(86.8 - 3n)/4
You can get this by combining the two. Make sure to give common denominators.
