csat-suneung 2015 Q17

csat-suneung · South-Korea · csat__math-A 4 marks Arithmetic Sequences and Series Find Specific Term from Given Conditions
For an arithmetic sequence $\left\{ a _ { n } \right\}$ satisfying $\sum _ { k = 1 } ^ { n } a _ { 2 k - 1 } = 3 n ^ { 2 } + n$, what is the value of $a _ { 8 }$? [4 points]
(1) 16
(2) 19
(3) 22
(4) 25
(5) 28
For an arithmetic sequence $\left\{ a _ { n } \right\}$ satisfying $\sum _ { k = 1 } ^ { n } a _ { 2 k - 1 } = 3 n ^ { 2 } + n$, what is the value of $a _ { 8 }$? [4 points]\\
(1) 16\\
(2) 19\\
(3) 22\\
(4) 25\\
(5) 28