Question

determine a soma dos termos de casa pa (-8 -5 -2...22)

Answer 1

(- 8, - 5, -2, ..., 22)

a₁ = - 8

r = - 5 - (- 8) ----- r = - 5 + 8 ----- r = 3

22 = - 8 + (n - 1) . 3 ----- 22 + 8 = (n - 1) . 3 ----- 30 = (n - 1) . 3

n - 1 = 30/3  ----- n - 1 = 10 ---- n = 10 + 1 ----- n = 11


S₁₁ = [(- 8 + 22) . 11]/2 ------- S₁₁ = [(14) . 11]/2 ---- S₁₁ = 154/2

S₁₁ = 77

Answer 2

Boa noite!
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A1 ⇒ -8
R ⇒ a2-a1  ⇒ -5 -(-8) ⇒ -5 + 8 = 3
An = 22
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An = a1 + (n-1)·r
22 = - 8 + (n-1)·3
22 = - 8 + 3n - 3
22-3n = - 8 - 3
-3n = -8-3-22
-3n = -11-22
-3n =  -33 (-1)
3n = 33
n = 33/3
n = 11
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Sn = (a1 + an ) · n
                2

S11 = (-8 + 22) · 11
                  2

S11 = 14 · 11
              2

S11 = 154
             2

S11 =  77
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Att;Guilherme Lima