№1 s₅: b(n) b₃=18 q=3 №2 (an) d=4 s₅₀=5500 a1=? - вопрос №1183245500131010507590718 от Doshatop 28.09.2020 13:27

Question

Алгебра: №1 s₅: b(n) b₃=18 q=3 №2 (an) d=4 s₅₀=5500 a1=? №3 (an) a₁=10 s₁₄=1050 d-?

Doshatop · Answer

1. b1•q^2=18b1•9=18b1=18/9=2 b1•(q^5–1) 2•242S5 = = = 242 q–1 2 2a1+49d2. S50 =•50=(2a1+49•4)•25= 2= (2a1+196)•25(2a1+196)•25=5500 |:252a1+196=2202a1=24a1=12 2a1+13d3. S14 = • 14 = (2a1+13d)•7 = 2= (2•10+13d)•7 = (20+13d)•7(20+13d)•7 = 1050 |:720+13d = 15013d = 130d = 10...