Which formula represents the nnn-th term of an arithmetic sequence?
an=a1+(n−1)da_n = a_1 + (n-1)dan=a1+(n−1)d
an=a1⋅rn−1a_n = a_1 \cdot r^{n-1}an=a1⋅rn−1
an=a1+nda_n = a_1 + ndan=a1+nd
an=n(a1+d)a_n = n(a_1 + d)an=n(a1+d)