Find ∑(5 – 2 k ) when k goes from 2 to 7.
-24
24
I am clueless
30
-18
7
∑(5 – 2 k ) = (5-4)+(5-6)+(5-8)+(5-10)+(5-12)+(5-14) = 1-1-3-5-7-9 = -24
k=2
Thanks
To find the sum of the expression ∑(5 – 2k) when k goes from 2 to 7, we can use the formula for the sum of an arithmetic series:
Sn = n/2 * (a + l)
where Sn is the sum of the series, n is the number of terms, a is the first term, and l is the last term.
In this case, the first term (a) is 5 - 2(2) = 5 - 4 = 1, and the last term (l) is 5 - 2(7) = 5 - 14 = -9. The number of terms (n) is determined by subtracting the first term from the last term and adding 1, so n = -9 - 1 + 1 = -9.
Now we can substitute these values into the formula:
Sn = n/2 * (a + l)
= -6/2 * (1 + -9)
= -3 * (-8)
= 24
Therefore, the sum of ∑(5 – 2k) when k goes from 2 to 7 is 24.