Question

the sequence -14, -9, -4, 1, ..., 41 has 12 terms. evaluate the related series.

Answer 1

The answer is 162.

sequence is arithmetic; d = 5

sum = (n/2)(a1+an)

an = a1 +d(n-1)

a12 = -14 + 5(11)

a12 = -14 + 55 ----> a12 = 41

sum: (12/2)(-14 + 41)
 = 6(27)
= 162