Write the mathematical expression that describes the arithmetic sequence.

Use sigma notation to describe the sum of the first ten terms of the arithmetic sequence
20, 18.5, 17, 15.5, 14, (the difference is from -1.5)
Help, please!

1 answer

term(n) = -1.5n +c
so when n = 1 your want term(1) to be 20
-1.5(1)n + c = 20
c = 21.5

term(n) = -1.5n + 21.5 , where n is a natural number

now just put that in the notation that you must have studied.