Question

9/10
what notation is used for the first term of an arithmetic sequence?
a sub 0
n sub 1
a sub 1
d sub 1

Explanation:

In standard arithmetic sequence notation, $a_n$ represents the $n$-th term. For the first term, $n=1$, so the notation is $a_1$ (read as "a sub 1"). $a_0$ is not the standard first term, $n_1$ is not used for sequence terms, and $d$ represents the common difference, not a term.

Answer:

a sub 1