Video Transcript
Find the sum of the terms of the
11-term arithmetic sequence whose first term is negative 92 and last term is
negative 102.
The first term 𝑎 of our arithmetic
sequence is equal to negative 92, and the last term 𝑙 is equal to negative 102. We are also told there are 11 terms
in the sequence. Therefore, 𝑛 is equal to 11. We could use this information to
calculate the common difference 𝑑. However, in this question, it is
not required. We can calculate the sum of the
first 𝑛 terms using the formula 𝑛 over two multiplied by 𝑎 plus 𝑙. Substituting in our values, we see
that 𝑆 sub 11 is equal to 11 over two multiplied by negative 92 plus negative
102. 11 divided by two is equal to 5.5,
and negative 92 plus negative 102 is equal to negative 194. Multiplying these two values gives
us negative 1067.
The sum of the 11 terms in the
arithmetic sequence whose first term is negative 92 and last term is negative 102 is
negative 1067.
