Question

UMA PROGRESSAO ARITIMETRICA DE 9 TERMOS TEM RAZAO 2 E A SOMA DE SEUS TERMOS E IGUAL A 0.DETERMINE O SEXTO TERMO DA PROGRESSAO

Answer 1

Resposta:

.$An = A1 + (n - 1)r\\\\A(9) = A1 + (9 - 1)2\\\\A(9) = A1 + 8.2\\\\A(9) = A1 + 16\\\\\\Sn = \frac{(A1 + An).n}{2} \\0 = \frac{(A1 + A1 + 16).9}{2} \\0 = \frac{(2a1 + 16).9}{2} \\0 = \frac{18a1 + 144}{2} \\0 = 9a1 + 72\\9a1 = -72\\a1 = \frac{-72}{9} \\a1 = -8,,\\\\\\A(6) = -8 + (6 - 1)2\\\\A(6) = -8 + 5.2\\\\\\A(6) = -8 + 10\\\\\\A(6) = 2$

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