Question

Aritmetika u3 adalah 18 dan u7 adalah 38. jumlah 24 suku pertama adalah

Answer 1

Mencari b = 38 - 18 / 7 - 3 = 20/4 = 5
Mencari a = 18 - (5 x 2) = 18 - 10 = 8

Jumlah 24 Suku Pertama = 24/2 x (2(8) + (24-1)5 )
12 x 131 = 1572

Answer 2

B = U7-U3 = 38-18 = 20 : (7-3=4) = 5
U3 = a + (n-1) b = 18
= a + (3-1) b = 18
= a + 2.b = 18
= a + 2.5 = 18
= a +10 = 18
= 18-10 = 8
Sn = n:2 (2a + (n-1) b)
S24 = 24:2 (2.8 + (24-1) 5 )
S24 = 12 (16+23.5 )
S24 = 12 (16+115)
S24 = 12.131
S24 = 1.572