maths
posted by sarah .
what is the nth term for the following sequence which begins
7, 11, 15, 19, 23

Is this an arithmetic progression (AP) or geometric progression (GP)?
AP's have constant differences, while GP's have constant ratios.
Given series:
7, 11, 15, 19, 23
differences:
117=4, 1511=4, 1915=4, 2319=4
(constant difference d=4, therefore AP)
ratios:
11/7, 15/11, 19/15, 23/19 (different, so NOT GP).
The nth term of an AP is:
A(n)=A(1)+(n1)d
d=4
A(n)=A(1)+(n1)d
=7+(n1)4
=7+4n4
=3+4n 
it just says work out the nth term for the those numbers

I hope you did not just read the first line of my response.
I was asking myself that question (hope you do the same). The rest of the response followed.