nomer 9 tolong bantuannya ya

jawabannya D ya. dipahami dan diteliti dulu. good luck

[tex]sn = \frac{n}{2} (2a + (n - 1)b) \\ 20 = \frac{5}{2} (2a + (5 - 1)1) \\ 40 = 5(2a + 4) \\ 40 = 10a + 20 \\ 40 - 20 = 10a \\ 20 = 10a \\ a = \frac{20}{10} \\ a = 2[/tex]
u1 = 2 + (1 -1) 1= 2 +0 = 2
u2 = 2 + (2 -1)1= 2 +1 = 3
u3 = 2 + (3-1)1 = 2 +2 =4

u1 × u2 × u3 = 2 × 3 ×4 = 24