9,-10,-29...U38.........?

U1 = 9
b = -19
Un = U1+(n-1)b
U38 = 9+(38-1)-19
= 9+(37)-19
= 9-703
= -694

9, -10, -29

U₁ = a = 9
b = -10 - 9 = -19

U₃₈ = a + (n - 1) x b
       = 9 + (38 - 1) x (-19)
      = 9 + 37 x (-19)
      = 9 - 703
      = -694

semoga jelas dan membantu ya