Diketahui suatu barisan aritmetika U2

Jawaban:

utk pers. 1

u2 + u3 = 26

(a + b) + (a + 2b) = 26

2a + 3b = 26

utk pers. 2

u7 – u2 = 20

(a + 6b) – (a + b) = 20

5b = 20

b = 4

cari a

2a + 3b = 26

2a + 3(4) = 26

2a = 26 – 12

2a = 14

a = 7

suku ke 21

un = a + ( n – 1 ) b

u21 = 7 + ( 21 – 1 ) 4

u21 = 7 + 20 x 4

u21 = 7 + 80

u21 = 87

Jawaban:

a

Penjelasan dengan langkah-langkah:

smg membntuuuu!!!!!