Tentukan suku ke-5 dan jumlah 5 suku pertama dan barisan dari: a. 20, 24, 28, .... b. 2, 6, 18, 54, ....

a. 20, 24, 28, ....
b. 2, 6, 18, 54, ....

a. U5 = a + 4b
= 20 + (4 × 4)
= 20 + 16 = 36

S5 = n/2 (2a + (n-1)b)
= 5/2 (2 × 20 + (4 × 4))
= 2,5 (40 + 16)
= 2,5 × 56 = 140

b. U5 = ar^n-1
= 2 × 3^4
= 2 × 81
= 162

S5 = a(r^n-1)/r-1
= 2( 3^5 - 1)/2
= 2 (242) / 2
= 242

Semoga membantu