1) 6,10,14,18….

By Posted on

Tentukan suku ke 10 dan deret ke 10.
2) 24,21,18,15….
Tentukan suku ke 35
Dan barisan ke 20​

1) 6,10,14,18….

Jawab:

1.) a = 6; b = 4; Un = a + b(n-1); Sn = n/2 (2a + b(n-1))

U10 = 6 + 4(10-1) = 6 +36 = 42

S10 = 10/2 (2.6 + 4(10-1)) = 5 (12 + 36) = 240

2.) a = 24; b = (-3)

U35 = 24 + (-3)(35-4) = 24 + (-93) = (-69)

S20 = 20/2 (2.24 + (-3)(20-1)) = 10 (48 + -57) = 10 (-9) = (-90)

Penjelasan dengan langkah-langkah: