Use sigma notation to represent the sum of the first seven terms of the following sequence: −4, −6, −8, …

Step-by-step explanation:

Arithmetic sequence:

In an arithmetic sequence, the difference of consecutive terms is always the same, called common difference.

The nth term of a sequence is given by:

In which is the first term and d is the common difference.

Sigma notation to represent the sum of the first seven terms

Sum going from the index starting at 1 and finishing at 7, that is:

Now we have to fund the function, which is given by an arithmetic sequence.

−4, −6, −8,

First term -4, common difference - 6 - (-4) = -6 + 4 = -2, so

Then

Sigma notation:

Replacing f(n)

:

step-by-step explanation: