Question

5.Diketahui Barisan Bilangan:3,7,11,15,19…
Nilai U20+U25=
A.178 C.99
B.158 D.79

6.Suatu Barisan Geometri Diketahui Suku Ke-5=1/4
Dan Suku Ke-7=1/16 Suku Pertamanya Adalah…
A. 1/2 C.2
B. 1 D.4

Answer 1

5. U20 = a + (n-1) b
= 3 + (20-1) 4
= 3 + 19 x 4
= 3 + 76
= 79

U25 = a + (n-1) b
= 3 + (25-1) 4
= 3 + 24 x 4
= 3 + 96
= 99

U20 + U25 = 79 + 99 = 178 (a)

6. a x r^5-1 = 1/4
a x r^4 = 1/4

a x r^7-1 = 1/16
a x r^6 = 1/16

a x r^6 = 1/16
a x r^4 = 1/4
dibagi menjadi
r² = 1/4
r = 1/2

a x r^4 = 1/4
a x 1/2^4 = 1/4
a x 1/16 = 1/4
a = 16/1 x 1/4
a = 4 (d)