csat-suneung 2011 Q26

csat-suneung · South-Korea · csat__math-humanities 3 marks Arithmetic Sequences and Series Compute Partial Sum of an Arithmetic Sequence
The sequence $\left\{ a _ { n } \right\}$ satisfies $$2 a _ { n + 1 } = a _ { n } + a _ { n + 2 }$$ for all natural numbers $n$. When $a _ { 2 } = - 1 , a _ { 3 } = 2$, what is the sum of the first 10 terms of the sequence $\left\{ a _ { n } \right\}$? [3 points]
(1) 95
(2) 90
(3) 85
(4) 80
(5) 75 
The sequence $\left\{ a _ { n } \right\}$ satisfies
$$2 a _ { n + 1 } = a _ { n } + a _ { n + 2 }$$
for all natural numbers $n$. When $a _ { 2 } = - 1 , a _ { 3 } = 2$, what is the sum of the first 10 terms of the sequence $\left\{ a _ { n } \right\}$? [3 points]\\
(1) 95\\
(2) 90\\
(3) 85\\
(4) 80\\
(5) 75
Paper Questions
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