if a1=1 and d=5, what is a5?

Question

I am struggling with understanding Arithmetic Sequence. Answers are greatly appreciated.

Answer 1

The recursive form of an arithmetic sequence is:

 

a_n = a_n-1 + d

 

So for a₁ = 1 and d = 5:

 

a₂ = a₁ + 5 = 1 + 5 = 6

 

a₃ = a₂ + 5 = 6 + 5 = 11

 

a₄ = a₃ + 5 = 11 + 5 = 16

 

a₅ =  _____?

 

Each term above is 5 more than the preceding term.  In general, we can write explicit form of the sequence as:

 

a_n = a₁ + (n-1)*d

 

So for a₁ = 1 and d = 5:

 

a₅ = 1 + (5-1)*5 = _____?