Question

Find the 88th term of the arithmetic sequence 21, 15, 9
and step by step how you solved it

Answer 1

• -501

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