cari u20 dari: 1.u8=64 U10=74 2.u9=81 u6=75 tolong yahh dengam cara

1) U₁₀ = 74 ; U₈ = 64 ; U₂₀ = ?

    U₁₀ = 74 = a + 9b
    U₈   = 64 = a + 7b
             ----------------- -
              10 = 2b ====> b = 5

    U₈ = 64 = a + 7(5)
            64 = a + 35 ===> a = 29

    U₂₀ = 29 + (19 x 5)
           = 29 + 95
           = 124

2) U₉ = 81 ; U₆ = 75 ; U₂₀ = ?

    U₉ = 81 = a + 8b
    U₆ = 75 = a + 5b
           ----------------- -
              6 = 3b ===> b = 2

     U₆ = 75 = a + 5(2)
             75 = a + 10 ===> a = 65

     U₂₀ = a + 19b
           = 65 + (19 x 2)
           = 65 + 38
           = 103

semoga jelas dan membantu ya

Mata pelajaran: Matematika
Materi: Barisan dan Deret

1. U8 = a + 7b = 64
U10 = a + 9b = 74
______________ _
-2b = -10
b = 5
a + 7(5) = 64
a + 35 = 64
a = 64 - 35
a = 29
Un = 5(1) + 24
U20 = 5(20) + 24
U20 = 124

2. U9 = a + 8b = 81
U6 = a + 5b = 75
_____________ _
b = 2
a + 8(2) = 81
a + 16 = 81
a = 81 - 16 = 65
Un = 2(1) + 63
U20 = 2(20) + 63
U20 = 163

Semoga membantu.