write the first 4 terms of this sequence

Question

a1 = 12 and an = an-1+4 for n is greater than or equal to 2.

Answer 1

If if understand correctly, the sequence is:

a₁=12 and a_n=a_n-1+4 for n greater than or equal to 2. If that's the case, we can just start plugging in the previous sequence value to get the next one:

 

For example, your formula a_n=a_n-1+4 gives you

a₂=a₁+4. And you know a₁=12, so

a₂=12+4=16

 

You can keep doing this to get as many terms of the sequence as you want! So

a₃=a₂+4, and from the previous step, you now have

a₃=16+4=20.

 

Let me know if you would like any more help!

Erika

Answer 2

a₁ = 12

a_n = a_n-1 + 4, with n ≥ 2 (this means 2 to positive infinity)

 

First let n = 2, in the equation:

 

a₂ = a_2-1 + 4

a₂ = a₁ + 4

a₂ = 12 + 4

a₂ = 16

 

You can repeat the process over and over to get up to the 4th term.

 

But understanding that this is an arithmetic sequence (the clue is the formula) a_n = a_n-1 + d, where 'd' is the difference of the sequence. Then you can just add 'd' or in this case, 4, to the succeeding terms.

 

a₁ = 12

a₂ = 16

a₃ = 20

a₄ = 24