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  1. Home
  2. 12th grade
  3. Precalculus
  4. Exercise : Find the term of an arithmetic sequence

Find the term of an arithmetic sequence Precalculus

Find the explicit term of the arithmetic sequence which first terms are the following.

-4, 2, 8, 14, 20, 26, 32, ...

We know that the following is the explicit formula of an arithmetic sequence whose first term is a_1 and common difference is d :

a_n= a_1+d\left(n-1\right)

Here, we have:

  • a_1 = -4
  • d=6

Therefore:

a_n = -4+6\left(n-1\right)\\= -4+6n-6\\=6n-10

The explicit form of this sequence is a_n=6n-10.

-3, 1, 5, 9, 13, 17, 21, ...

We know that the following is the explicit formula of an arithmetic sequence whose first term is a_1 and common difference is d :

a_n= a_1+d\left(n-1\right)

Here, we have:

  • a_1 = -3
  • d=4

Therefore:

a_n = -3+4\left(n-1\right)\\= -3+4n-4\\=4n-7

The explicit form of this sequence is a_n=4n-7.

3, 10, 17, 24, 31, 38,...

We know that the following is the explicit formula of an arithmetic sequence whose first term is a_1 and common difference is d :

a_n= a_1+d\left(n-1\right)

Here, we have:

  • a_1 = 3
  • d=7

Therefore:

a_n = 3+7\left(n-1\right)\\= 3+7n-7\\=7n-4

The explicit form of this sequence is a_n=7n-4.

10, 7 ,4 ,1 ,-2 ,...

We know that the following is the explicit formula of an arithmetic sequence whose first term is a_1 and common difference is d :

a_n= a_1+d\left(n-1\right)

Here, we have:

  • a_1 = 10
  • d=-3

Therefore:

a_n = 10-3\left(n-1\right)\\= 10-3n+3\\=-3n+13

The explicit form of this sequence is a_n=-3n+13.

101, 97, 93, 89, 85, 81,...

We know that the following is the explicit formula of an arithmetic sequence whose first term is a_1 and common difference is d :

a_n= a_1+d\left(n-1\right)

Here, we have:

  • a_1 =101
  • d=-4

Therefore:

a_n = 101-4\left(n-1\right)\\= 101-4n+4\\=-4n+105

The explicit form of this sequence is a_n=-4n+105.

-17, -14, -11, -8, -5, -2,...

We know that the following is the explicit formula of an arithmetic sequence whose first term is a_1 and common difference is d :

a_n= a_1+d\left(n-1\right)

Here, we have:

  • a_1 = -17
  • d=3

Therefore:

a_n = -17+3\left(n-1\right)\\= -17+3n-3\\=3n-20

The explicit form of this sequence is a_n=3n-20.

21, 14, 7, 0, -7, ...

We know that the following is the explicit formula of an arithmetic sequence whose first term is a_1 and common difference is d :

a_n= a_1+d\left(n-1\right)

Here, we have:

  • a_1 =21
  • d=-7

Therefore:

a_n = 21-7\left(n-1\right)\\= 21-7n+7\\=-7n+28

The explicit form of this sequence is a_n=-7n+28.

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See also
  • Course : Sequences
  • Exercise : Determine whether a any sequence defined by a graph increases, decreases or is not monotonic
  • Exercise : Convert an arithmetic sequence between recursive and explicit form
  • Exercise : Find the term of a geometric sequence
  • Exercise : Convert a geometric sequence between recursive and explicit form
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