Question

Diketahu suatu barisan aritmetika dengan U2=35 dan U6=43. Suku ke-18 adalah...
A.51
B.67
C.69
D.84

Answer 1

A + b = 35 (Suku kedua)
a + 5b = 43 (Suku keenam)
----------------- --(Dikurangi)
-4b = - 8
b = 2
a + b = 35
a + 2 = 35
a = 33
Suku ke delapan belas = a + 17b = 33 + 17(2) = 33 + 34 = 67

Answer 2

U2 = a + b = 35
U6 = a + 5b = 43

diketahui :

a + b = 35
a+ 5b = 43 -
--------------------
-4b = -8
b = -8 ÷ -4
b = 2

subsitusikan b
a + b = 35
a + 2 = 35
a = 35-2
a = 33

Maka suku ke 18

U18 = a +(n-1)b
U18 = 33 + (18-1)2
U18 = 33 + 17 .2
U18 = 33 +34
U18 = 67