Question

Tolong bantuin ya kak

Answer 1

Un = a + (n - 1) b
U₂ = a + (2 - 1) b
U₂ = a + b = 32 ....(1)

U₅ = a + (5 - 1) b
U₅ = a + 4 b = 20 ....(2)

a + 4 b = 20
a + b + 3 b = 20
32 + 3b = 20
3 b = 20 - 32
b = - 12 / 3
b = - 4

a + b = 32
a + (- 4) = 32
a = 32 +4
a = 36

Sn = n / 2 { 2a + (n - 1) b }
S₇ = 7 / 2 { 2 . 36 + (7 - 1) -4 }
S₇ = 7 / 2 (72 - 24)
S₇ = 7 / 2 . 48
S₇ = 7 . 24
S₇ = 168

Umur ke 7 anak tsb = 36, 32, 28, 24, 20, 16, 12

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