Diketahui U4 =26 dan U8 =34. Ditanya b? a? U100?

Un = bn + a - b
U4 = 4b + a - b
26  = 3b + a

Un = bn + a - b
U8 = 8b + a - b
34 = 7b + a

26 = 3b + a
34 = 7b + a
---------------- -
-8  = -4b
  b  = -8/-4
  b  = 2

26 = 3b + a
26 = 3(2) + a
26 = 6 + a
  a = 26 - 6
  a = 20

    Un = bn + a - b
U100 = 2(100) + 20 - 2
          = 200 + 18
          = 218

U4 = a + 3b = 26
U8 = a + 7b = 34
_____________
-4b = -8
b = 2

a + 3b = 26
a + 3(2) = 26
a + 6 = 26
a = 20

U100 = a + 99b
U100 = 20 + 99(2)
U100 = 20 + 198
U100 = 218

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