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Which recursive sequence would produce the sequence 
1,-2,-11,dots ?

a_(1)=1 and 
a_(n)=2a_(n-1)-4

a_(1)=1 and 
a_(n)=3a_(n-1)-5

a_(1)=1 and 
a_(n)=-5a_(n-1)+3

a_(1)=1 and 
a_(n)=-4a_(n-1)+2

Which recursive sequence would produce the sequence 1,2,11, 1,-2,-11, \ldots ?\newlinea1=1 a_{1}=1 and an=2an14 a_{n}=2 a_{n-1}-4 \newlinea1=1 a_{1}=1 and an=3an15 a_{n}=3 a_{n-1}-5 \newlinea1=1 a_{1}=1 and an=5an1+3 a_{n}=-5 a_{n-1}+3 \newlinea1=1 a_{1}=1 and an=4an1+2 a_{n}=-4 a_{n-1}+2

Full solution

Q. Which recursive sequence would produce the sequence 1,2,11, 1,-2,-11, \ldots ?\newlinea1=1 a_{1}=1 and an=2an14 a_{n}=2 a_{n-1}-4 \newlinea1=1 a_{1}=1 and an=3an15 a_{n}=3 a_{n-1}-5 \newlinea1=1 a_{1}=1 and an=5an1+3 a_{n}=-5 a_{n-1}+3 \newlinea1=1 a_{1}=1 and an=4an1+2 a_{n}=-4 a_{n-1}+2
  1. Test Recursive Formula: Let's start by testing each given recursive formula with the initial value a1=1a_{1}=1 to see which one produces the sequence 1,2,11,1, -2, -11, \ldots .\newlineWe will begin with the first option:\newlinea1=1a_{1}=1 and \newlinean=2an14a_{n}=2a_{n-1}-4\newlineWe need to calculate a2a_{2} using the initial value a1=1a_{1}=1.\newlinea2=2a14a_{2}=2a_{1}-4\newlinea2=2(1)4a_{2}=2(1)-4\newlinea2=24a_{2}=2-4\newlinea2=2a_{2}=-2\newlineSo far, the sequence matches: 1,2,11,1, -2, -11, \ldots 00. Now let's calculate 1,2,11,1, -2, -11, \ldots 11.\newline1,2,11,1, -2, -11, \ldots 22\newline1,2,11,1, -2, -11, \ldots 33\newline1,2,11,1, -2, -11, \ldots 44\newline1,2,11,1, -2, -11, \ldots 55\newlineThe third term we calculated is 1,2,11,1, -2, -11, \ldots 66, but the third term in the given sequence is 1,2,11,1, -2, -11, \ldots 77. Therefore, this recursive formula does not produce the given sequence.

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