Question

Kak tolong jawab!! besok dikumpulin..

Answer 1

Un = bn + a - b
U5 = 5b + a - b
13  = 4b + a

Un = bn + a - b
U9 = 9b + a - b
21  = 8b + a

13 = 4b + a
21 = 8b + a
---------------- -
-8  = -4b 
  b = -8/-4
  b = 2

13 = 4b + a
13 = 4(2) + a
13 = 8 + a
 a  = 13 - 8
 a  = 5

a) beda = 2

b) Un = bn + a - b
   U10= 2(10) + 5 - 2
          = 20 + 3
          = 23

c) Sn = n/2 (2a + (n-1)b)
   S11 = 11/2 (2.5 + (11-1)2)
          = 11/2 (10 + 20)
          = 11/2 x 30
          = 165