Question

Deret aritmetika teridiri dari 10 suku
jumlah suku 1+suku 2 = 9
jumlah suku 5+suku 6 = 33
jumlah deret tsb?

Answer 1

U1 = a
u2 = a+b
u5 = a+4b
u6= a+5b

2a+b     = 9
2a + 9b = 33  -
-8b = -24
b = 3

2a+b = 9
2a+3 = 9
2a = 6
a=3

s10 = 5 (6 + 9.3)
s10 = 5.33
s10= 165

Answer 2

U1 = a
U2 = a + b
U1 + U2 = 2a + b = 9
U5 = a + 4b
U6 = a + 5b
U5 + U6 = 2a +9b = 33

2a + b = 9
2a + 9b = 33
-8b = -24
b = 3

2a + b = 9
2a + 3 = 9
2a = 6
a = 3

S10 = 10/2 (2.3+(10-1)3)
= 5 (6+27) = 165