csat-suneung 2011 Q4

csat-suneung · South-Korea · csat__math-humanities 2 marks Geometric Sequences and Series Determine the Limit of a Sequence via Geometric Series
When $\lim _ { n \rightarrow \infty } \frac { a \times 6 ^ { n + 1 } - 5 ^ { n } } { 6 ^ { n } + 5 ^ { n } } = 4$, what is the value of the constant $a$? [2 points]
(1) $\frac { 1 } { 3 }$
(2) $\frac { 1 } { 2 }$
(3) $\frac { 2 } { 3 }$
(4) $\frac { 4 } { 3 }$
(5) $\frac { 3 } { 2 }$
When $\lim _ { n \rightarrow \infty } \frac { a \times 6 ^ { n + 1 } - 5 ^ { n } } { 6 ^ { n } + 5 ^ { n } } = 4$, what is the value of the constant $a$? [2 points]\\
(1) $\frac { 1 } { 3 }$\\
(2) $\frac { 1 } { 2 }$\\
(3) $\frac { 2 } { 3 }$\\
(4) $\frac { 4 } { 3 }$\\
(5) $\frac { 3 } { 2 }$