Question

Find the sum of the arithmetic series -1+ 2+5+8+... where n=7.A. 56B. 184C. 92D. 380Reset Selection

Answer 1

Answer:

Step-by-step explanation:

The arithmetic series is:

-1 + 2 + 5 + 8 + .....

The first term, a = -1

The common difference, d = 2 - (-1)

d = 3

The number of terms, n = 7

Find the sum of the arithmetic series below

`\begin{gathered} S_n=(n)/(2)[2a+(n-1)d] \\ \\ S_7=(7)/(2)[2(-1)+(7-1)(3)] \\ \\ S_7=(7)/(2)(-2+18) \\ \\ S_7=(7)/(2)(16) \\ \\ S_7=56 \end{gathered}`

Therefore, the sum of the arithmetic series = 56