Write this arithmetic series with summation notation: 25, 21, 17, 13 …; 8 terms.

Answer 1

The sequence is arithmetic with common difference d = -4

a_n = a₁ + (n-1)(-4) = 25 - 4n + 4 = 29 - 4n

So, 25 + 21 + 17 + 13 + 9 + 5 + 1 - 3 = ∑_{(n= 1 to 8)} (29 - 4n)

Answer 2

Keep subtracting 4..................