Tolong dijawabkan....

Penyelesaian:

1. tentukan S10 dari tiap-tiap barisan bil dibawah:
a. 3 + 10 + 17 + 24 + ...
a = 3
b = 7

Sn = n/2(2a+(n-1)b
= 10/2(2(3) + (10-1)7)
= 5(6 + 63)
= 5(69)
= 345

b. 38 + 33 + 28 + 23 + ...
a = 38
b = -5

Sn = n/2(2a+(n-1)b
= 10/2(2(38) + (10-1)(-5)
= 5(76 - 45)
= 155

c. -5 + (-10) + (-15) + (-20) + ...
a = -5
b = -5

Sn = n/2(2a+(n-1)b
= 10/2(2(-5) + (10-1)(-5)
= 5(-10 - 45)
= -275

d. 1/2 + 1 + 2 + 4 + ...
a = 1/2
r = 2

Sn = a(1-r^n) / 1-r
= 1/2(1 - 2^10) / 1 - r
= 1/2(1 - 1024) / 1 - 2
= -1/2(-1023)
= 511,5

e. 3 + 2 + 4/3 + 8/9 + ...
a = 3
r = 2/3

Sn = a(1 - r^n) / 1 - r
= 3(1 - (2/3)^10) / 1 - 2/3
= 9(1 - 1024/59049)
= 9(58025/59049)
= 58025/6561

f. 4 + 6 + 9 + 27/2 + ...
a = 4
r = 3/2

Sn = a(1 - r^n) / 1 - r
= 4(1 - (3/2)^10) / 1 - r
= 4(1 - 59049/1024) / 1 - 3/2
= -8(-58025/1024)
= 58025/128

2. barisan bilangan: 1 + 2 + 4 + 8 + ... + 2^n-1 = 127
a = 1
r = 2

Sn = a(1 - r^n) / 1 - r
127 = 1(1 - 2^n-1) / -1
127 = -1(1 - 2^n . 1/2)
127 = -1 - 2^n . 1/2
128 = 2^n . 1/2
2^n = 256
2^n = 2^8
n = 8