Jawaban suku ke-21 barisan aritematika 4,1,-2,-5...adalah

Mapel : Matematika
Bab : Barisan dan Deret

a = 4
b = 1 - 4 = -3

  Un = bn + a - b
U21 = -3.21 + 4 - (-3)
        = -63 + 4 + 3
        = -63 + 7
        = -56

a = 4
b = 1 - 4 = - 3

Un = a + ( n - 1 ) b
U21 = 4 + ( 21 - 1 ) (-3)
= 4 + (20 × -3)
= 4 + (-60)
= (-56)