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jawab

1.
7
Σ  n³  = 3³ + 4³ + 5³ + 6³ +7³ = 775
n= 3

n = 3 → n³ = 3³ = 27 
n = 4 → n³ = 4³ = 64
n = 5 → n³ = 5³ = 125
n = 6 → n³ = 6³ = 216
n = 7 → n³ = 7³ = 343
jumlah= 775

5
Σ  1/2 n (n+1)² = 2 + 9 + 24+ 50 + 80 = 165
n = 1

S=1/2 (n)(n+1)² 
n = 1 →s = 1/2(1)(1+1)² = 1/2 (1)(2)² = 1/2 (4)= 2
n = 2 →s = 1/2(2)(3)² = 9
n = 3 →s = 1/2(3)(4)² = 24
n = 4 →s = 1/2(4)(5)² = 50
n = 5 →s = 1/2(5)(6)² = 80
jumlah = 165

 Tanda Σ  artinya Jumlah/ penjumlaan