tolong dibantu yaa..soalnya dikumpulkan besok

3. Un = a + (n-1) b
U33 = 4+(33-1)3
=4+(32)3
=4+96
=100


moga bermanfaat

1. diketahui
n = 5
u1 = 12
u5= 192

cari rasio terlebihdahulu

un = a . r^n-1
u5 = a . r^4
192 = 12 . r^4
192/12 = r^4
16 = r^4
2 = r


seingga panjang tali mula2 (sn)

sn = a(r^n -1)/(r-1)
s5 = 12(2^5 -1) / (2-1)
= 12(32 - 1 )
= 12 . 31
= 372 cm


2. kelipatan 3 antara 100 .... 300
105, 108, 112, ..... 225

a = 105
b = 3

ditanya sn

cari n(banyak suku terlebih dahlu)

un = a+(n-1)b
225 = 105 +(n-1)3
225-105 = 3n-3
120 = 3n-3
120+3 = 3n
123 = 3n
n = 41

sn = n/2(a+un)
s41 = 41/2(105+41)
= 41/2 (146)
= 2993

3.
4,7,10,13

a = 4
b 3

u33 = a+(n-1)b
= 4+(33-1)3
= 4 + 32.3
= 4 + 96
=100