Ответы на вопрос:
Sn = (2a1 + (n-1)d)n/2 s3 = (2a1 +2d)3/2 = 0 2a1 + 2d = 0 an = a1 + (n-1)d a4 = a1 + 3d a5 = a1 + 4d a6 = a1 + 5d a4+a5+a6 = a1 + 3d+ a1 + 4d + a1 + 5d = 3a1 + 12d = 18 система 2a1 + 2d = 0 и 3a1 + 12d = 18 a1 + d = 0 a1+ 4d = 6 a1 = -d -d + 4d = 6 3d = 6 d = 2 a1 = -2 a6 = -2 + 5*2 = -2 + 10 = 8 2) an = a1 + (n-1)d a6 = a1 + 5d a9 = a1 + 8d система a1 + 5d = 15 a1 + 8d = 21 a1 = 15 - 5d 15 - 5d + 8d = 21 3d = 6 d = 2 a1 = 15 - 2*5 = 5 a16 = 5 + 2*15 = 5 + 30 = 35
Популярно: Математика
-
ruslanlezgi12.02.2023 16:09
-
66666666ak25.06.2020 23:52
-
seregatarlykov02.05.2020 23:33
-
lox5309.03.2021 12:04
-
Алёна1657805.08.2021 00:06
-
plesovskih30.08.2022 18:43
-
Yulchan2319.02.2023 13:34
-
айка39720.07.2020 09:42
-
Ашка123110.04.2021 11:02
-
stockmen07.04.2023 08:56