Question

Tentukan jumlah 10 suku pertama dari barisan bilangan berikut ini :
a. 3+10+17+24+....
b. 38 + 33 + 28 + 23 + ...
c. -5 + (-10) + (-15) + (-20) +...
d. 1/2 + 1 + 2 + 4 +..
e. 3+ 2 + 4/2 + 8/9 + ...
f. 4 + 6 + 9 + 27/2 + ....

Answer 1

a. 3+10+17+24+....
s10 = 10/2 ( 6 + 9(7)) = 10/2 (69)= 345

b. 38 + 33 + 28 + 23 + ...
s10 = 10/2(76+9(-5)) = 5(76-45)= 155

c. -5 + (-10) + (-15) + (-20) +...
s10 = 10/2 {-10 +9(-5)} = 5 {-55)= -275

d. 1/2 + 1 + 2 + 4 +..
a = 1/2
r = 2
s10 = (1/2) (2^10-1) /(2-1) = 1/2 (1023)= 511,5

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

f. 4 + 6 + 9 + 27/2 + ....
a = 4
r = 3/2
s10 = 4 ( (3/2)^10 - 1 )/( 3/2 - 1)
s10 = 8 ( 3/2 ^10 - 1)

Answer 2

A.rumus=3+(nx7)-7=3+(10x7)-7=(3+70)-7=73-7=66
b.rumus=38-(nx7)=38-(10x7)=38-70=-32
c.rumus=-5+(nx(-5))-(-5)=-5+(10x(-5))-(-5)=(-5+(-50)-(-5)=-55-(-5)=-50
Maaf ya hanya bisa menjawab 3 nomor...........