Question

What is the sum of the terms of the series (-1) + (-2) + (-3) +... + (-10)?

A. -110

B. -55

C. -22

Answer 1

Answer:

$S_{10}=-55$

Step-by-step explanation:

The given series is

$(-1)+(-2)+(-3)+...+(-10)$

The first term of this arithmetic sequence is

$a_1=-1$ the last term is  $l=-10$

The sum of the first n-terms is given by

$S_n=\frac{n}{2}(a_1+l)$

The first 10 terms is

$S_{10}=\frac{10}{2}(-1+-10)$

$S_{10}=5(-11)$

$S_{10}=-55$