Okay, I need to find the 101th term of the sequence 5,9,13,17,21...

Question

Do I do this:
a1 + (n-1)d

SO...
5+(101-1)4
5+(100)4
105x4
420

Did I do this problem correctly?

Answer 1

Almost!

First, check your formula against values:
a1+(n-1)d
where a1=5, d=4, and n=term number
For the first term, n=1
5+(1-1)*4=5 correct
For the third term:
5+(3-1)*4=5+2*4=13 correct.
So there is a good chance the formula.

Now do the calculations for the 101th term:
5+(101-1)*4
=5+100*4
Remembering that in all calculations, the priority of operations is in the order:
()
* or ÷
+ or -

So we need to multiply before add, or
5+100*4
=5 + (100*4)
=5 + 400
= 405