The first term of an arithmetic sequence is $a$ and the common difference is $d$. The sum of the first $n$ terms is denoted by $S _ { n }$. If $S _ { 8 } > 3 S _ { 6 }$, what can be deduced about the sign of $a$ and the sign of $d$ ?
& E & 12 & F
The first term of an arithmetic sequence is $a$ and the common difference is $d$.
The sum of the first $n$ terms is denoted by $S _ { n }$.
If $S _ { 8 } > 3 S _ { 6 }$, what can be deduced about the sign of $a$ and the sign of $d$ ?