Question

Pada barisan aritmetika diketahui bahwa u5 :13 dan u7:17 tentukan jumlah 10 suku pertama barisan tersebut

Answer 1

U5 = a + 4b = 13
a = 13- 4b

U7 = a + 6b = 17
13 - 4b + 6b = 17
2b = 17 - 13
b = 2

U5 = a + 4b = 13
a = 13 - 8 = 5

U10 = a + 9b = 5 + 9.2
= 5 + 18 = 23

S10 = 10\2 (5 + 23)
= 5 . 28 = 140