Question

NEED HELP ASAP!!!!!!!!!!!!!!!!      

Answer 1

An=a1+d(n-1)
a1=first term
an=nth term
d=common differnce or how much it increases by each time
n=which one


so
originally 3 trees
a1=3

and after 19 years, 84 trees, so a19=84

a19=84=3+d(19-1)
84=3+d(18)
minus 3 both sides
81=18d
divide both sides by 18
4.5=d


an=3+4.5(n-1) or
an=4.5n-1.5
or
t(n)=3+4.5(n-1) or
t(n)=4.5n-1.5