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Question 8 (5 points)

Find the sum of [tex]\sum_{k=1}^6(3-k)[/tex].

A. 2
B. -3
C. 0


Sagot :

To solve the problem of finding the sum [tex]\(\sum_{k=1}^6 (3 - k)\)[/tex], let's break it down step-by-step.

1. Identify the given expression for each term in the sum:

We are given the expression [tex]\((3 - k)\)[/tex] where [tex]\(k\)[/tex] takes on successive integer values starting from 1 up to 6.

2. Calculate each term individually for [tex]\(k\)[/tex] from 1 to 6:

- When [tex]\(k = 1\)[/tex]: [tex]\(3 - 1 = 2\)[/tex]
- When [tex]\(k = 2\)[/tex]: [tex]\(3 - 2 = 1\)[/tex]
- When [tex]\(k = 3\)[/tex]: [tex]\(3 - 3 = 0\)[/tex]
- When [tex]\(k = 4\)[/tex]: [tex]\(3 - 4 = -1\)[/tex]
- When [tex]\(k = 5\)[/tex]: [tex]\(3 - 5 = -2\)[/tex]
- When [tex]\(k = 6\)[/tex]: [tex]\(3 - 6 = -3\)[/tex]

3. Sum these values together:

[tex]\[ 2 + 1 + 0 - 1 - 2 - 3 \][/tex]

4. Combine the terms:

[tex]\[ 2 + 1 = 3 \][/tex]
[tex]\[ 3 + 0 = 3 \][/tex]
[tex]\[ 3 - 1 = 2 \][/tex]
[tex]\[ 2 - 2 = 0 \][/tex]
[tex]\[ 0 - 3 = -3 \][/tex]

So, the sum [tex]\(\sum_{k=1}^6 (3 - k)\)[/tex] is [tex]\(-3\)[/tex].

Among the given options, the correct answer is:

B) [tex]\(-3\)[/tex].