Tolong dong nomer enam

Semogaa membantu yaaaaaaa☺️

Bab Barisan dan Deret
Matematika SMP Kelas IX

Aritmatika

2 . U2 = U1 + U3
2 . (x + 2) = (2x + 1) + (2x - 3)
2x + 4 = 4x - 2
2x - 4x = -2 - 4
-2x = -6
x = -6/-2
x = 3

U1 = 2x + 1
U1 = 2 . (3) + 1
U1 = 7

U2 = x + 2
U2 = 3 + 2
U2 = 5

U3 = 2x - 3
U3 = 2 . (3) - 3
U3 = 3

7, 5, 3, ...

b = U2 - U1
b = 5 - 7
b = -2

U15 = a + 14 b
U15 = 7 + 14 . (-2)
U15 = 7 - 28
U15 = -21

jawabannya C