This is an arithmetic sequence because each term is 7 greater than the previous term, so 7 is what is called the common difference...
Any arithmetic sequence can be expressed as:
a(n)=a+d(n-1), a=first term, d=common difference, n=term number.
We know a=1 and d=7 so:
a(n)=1+7(n-1)
a(n)=1+7n-7
a(n)=7n-6
The above is the "rule" for the nth term.
It's 3x+2 because 3 ÷2 is 6 so it's 3x+2
