I'm not understanding which statement is correct, to me they all look wrong
2 answers:
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An=a1+d(n-1)
an=nth term
a1=first term, when n=1
d=common differnce=amount each term increases by
n=which one
so
when n=1, an=40
so a1=40
it seems to increas by 7 each time
an=40+7(n-1)
explicit formula is expanded
an=40+7n-7
an=33+7n is the formula
the domain is natural numbers because you can't have the -3rd term or the 0th term or the 3.24th term
domain is natural numbers
the formula is
or 
an=nth term
a1=first term, when n=1
d=common differnce=amount each term increases by
n=which one
so
when n=1, an=40
so a1=40
it seems to increas by 7 each time
an=40+7(n-1)
explicit formula is expanded
an=40+7n-7
an=33+7n is the formula
the domain is natural numbers because you can't have the -3rd term or the 0th term or the 3.24th term
domain is natural numbers
the formula is