Question

ESSAY (SMP kls 9)
tentukan enam suku pertama suatu barisan bilangan, bila rumus suku ke n barisannya adalah:
a. = n(5-2n)
b. = n(n+3)
c. = 2n(n-1)
d. = n(n-1)/2
e. = / n+1

Answer 1

A. =  1 (5 - 2×1) = 1 ( 5 - 2) = 1 × 3 = 3
=  2 (5 - 2×2) = 2 ( 5 - 4) = 2 × 1= 2
=  3 (5 - 2×3) = 3 ( 5 - 6) = 3 × (-1) = -3
=  4 (5 - 2×4) = 4 ( 5 - 8) = 4 × (-3) = -12
=  5 (5 - 2×5) = 5 ( 5 - 10) = 5 × (-5) = -25
=  6 (5 - 2×6) = 6 ( 5 - 12) = 6 × (-7) = -42

b. = 1(1 + 3) = 1 × 4 = 4
= 2(2 + 3) = 2 × 5 = 10
= 3(3 + 3) = 3 × 6 = 18
= 4(4 + 3) = 4 × 7 = 28
= 5(5 + 3) = 5 × 8 = 40
= 6(6 + 3) = 6 × 9 = 54

c. = 2×1(1 - 1) = 2×0 = 0
= 2×2(2 - 1) = 4×1 = 4
= 2×3(3 - 1) = 6×2 = 12
= 2×4(4 - 1) = 8×3 = 24
= 2×5(5 - 1) = 10×4 = 40
= 2×6(6 - 1) = 12×5 = 60

d. = 1(1 - 1) /2 = 1×0 /2 = 0/2 = 0
= 2(2 - 1) /2 = 2×1 /2 = 2/2 = 1
= 3(3 - 1) /2 = 3×2 /2 = 6/2 = 3
= 4(4 - 1) /2 = 4×3 /2 = 12/2 = 6
= 5(5 - 1) /2 = 5×4 /2 = 20/2 = 10
= 6(6 - 1) /2 = 6×5 /2 = 30/2 = 15

e. = /(1 + 1) = 1/2
= /(2 + 1) = 4/3 = 1 1/3
= /(3 + 1) = 9/4 = 1 1/9
= /(4 + 1) = 16/5 = 3 1/5
= /(5 + 1) = 25/6 = 4 1/5
= /(6 + 1) = 36/7 = 5 1/7