Respuesta :

Answer:

  • -501

Step-by-step explanation:

The given sequence is :

21, 15, 9, ...

Finding the common difference (d)

  • d = Term - previous term
  • d = 15 - 21
  • d = -6

Formula for the nth term of a sequence

  • aₙ = a + (n - 1)d
  • a = first term = 21 (in this case)
  • n = number of terms
  • d = common difference = -6

Taking n = 88 as we are asked to find the 88th term :

  • a₈₈ = 21 + (88 - 1)(-6)
  • a₈₈ = 21 + 87(-6)
  • a₈₈ = 21 - 522
  • a₈₈ = -501