Respuesta :

Ckaranja
This is an aritmetic series;
a=-10
d=-7--10
d=3
n= 7
Sum=[tex] \frac{n}{2} [/tex](2a+(n-1)d)
Sum=[tex] \frac{7}{2} (2*(-10)+(7-1)3)[/tex]
sum=3.5(-20+18)
sum=3.5(-2)
sum=-7

Answer:

d -7

Step-by-step explanation:

The sum of an arithmetic sequence Sn whose first and last terms are known may be expressed as

Sn = n/2(a + l)

where a and l are the first and last terms of the arithmetic sequence with n number of terms

Thus for the  given sequence, the sum Sn is

S₇ = 7/2 (-10 + 8)

Since there are 7 terms in the sequence

= 3.5 * -2

= -7

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