made easy [closed]

Question

let an be the recurrenence relation which satisfies $a_{n}=4(a_{n-1}-a_{n-2})$ with $a_{1}$=2 and $a_{2}=8$.

let X corresponds to the value of $a_{17}$.then values of $log_{2}(\left | x \right |)$ will be _____?

 

am getting 18.

Comments

21.1?

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yes but how??i am very confused

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solve this by characteristic equation method

above equation can be represent as - $r^{2}-4r+4=0$