tolong dong no 1 a dan f dan no 2, kelas 9

1a.]
3 + 10 + 17 + 24 + ... [Baris Aritmatika]

a = 3
b = 10 - 3 = 7

Un = a + (n - 1)b
U₁₀ = a + 9b
U₁₀ = 3 + 9(7)
U₁₀ = 66

Sehingga
Sn = ⁿ/₂ (a + Un)
S₁₀ = ¹⁰/₂ (3 + 66)
S₁₀ = 5(69)
S₁₀ = 345

1f.]
4 + 6 + 9 + ²⁷/₂ + ... [Baris Geometri]
a = 4
r = 6 : 4 = ³/₂

Sn = a(rⁿ - 1) / (r - 1)
S₁₀ = 4( [³/₂]¹⁰ - 1) / (³/₂ - 1)
S₁₀ = 4 ( ⁵⁸⁰²⁵/₁₀₂₄ ) / (½)
S₁₀ = 453 ⁴¹/₁₂₈

2.]
1 + 2 + 4 + 8 + ... + 2ⁿ⁻¹ = 127
a = 1
r = 2 : 1 = 2

Sn = a(rⁿ - 1) / (r - 1)
127 = (2ⁿ - 1) / (2 - 1)
127 = 2ⁿ - 1
128 = 2ⁿ
n = 7