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Which recursive sequence would produce the sequence 
1,-2,13,dots ?

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

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

Which recursive sequence would produce the sequence 1,2,13, 1,-2,13, \ldots ?\newlinea1=1 a_{1}=1 and an=4an1+2 a_{n}=-4 a_{n-1}+2 \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

Full solution

Q. Which recursive sequence would produce the sequence 1,2,13, 1,-2,13, \ldots ?\newlinea1=1 a_{1}=1 and an=4an1+2 a_{n}=-4 a_{n-1}+2 \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
  1. Calculate Second Term: To determine which recursive sequence produces the given sequence, we will calculate the second term using each of the provided recursive formulas and compare it to the second term in the sequence, which is 2-2.
  2. First Recursive Formula: Using the first recursive formula: a1=1a_{1}=1 and an=4an1+2a_{n}=-4a_{n-1}+2. We calculate the second term: a2=4a1+2=4×1+2=4+2=2a_{2}=-4a_{1}+2 = -4\times1+2 = -4+2 = -2. This matches the second term of the given sequence.
  3. Calculate Third Term: We will now calculate the third term using the same formula to see if it matches the third term of the sequence, which is 1313. \newlinea3=4a2+2=4(2)+2=8+2=10.a_{3}=-4a_{2}+2 = -4*(-2)+2 = 8+2 = 10. \newlineThis does not match the third term of the given sequence, so this recursive formula is incorrect.
  4. Second Recursive Formula: Using the second recursive formula: a1=1a_{1}=1 and an=2an14a_{n}=2a_{n-1}-4. We calculate the second term: a2=2a14=2×14=24=2a_{2}=2a_{1}-4 = 2\times1-4 = 2-4 = -2. This matches the second term of the given sequence.
  5. Calculate Third Term: We will now calculate the third term using the same formula to see if it matches the third term of the sequence, which is 1313. \newlinea3=2a24=2(2)4=44=8.a_{3}=2a_{2}-4 = 2*(-2)-4 = -4-4 = -8. \newlineThis does not match the third term of the given sequence, so this recursive formula is also incorrect.
  6. Third Recursive Formula: Using the third recursive formula: a1=1a_{1}=1 and an=3an15a_{n}=3a_{n-1}-5. We calculate the second term: a2=3a15=3×15=35=2a_{2}=3a_{1}-5 = 3\times1-5 = 3-5 = -2. This matches the second term of the given sequence.
  7. Calculate Second Term: We will now calculate the third term using the same formula to see if it matches the third term of the sequence, which is 1313. \newlinea3=3a25=3(2)5=65=11.a_{3}=3a_{2}-5 = 3*(-2)-5 = -6-5 = -11.\newlineThis does not match the third term of the given sequence, so this recursive formula is also incorrect.
  8. Fourth Recursive Formula: Using the fourth recursive formula: a1=1a_{1}=1 and an=5an1+3a_{n}=-5a_{n-1}+3. We calculate the second term: a2=5a1+3=5×1+3=5+3=2a_{2}=-5a_{1}+3 = -5\times1+3 = -5+3 = -2. This matches the second term of the given sequence.
  9. Calculate Third Term: We will now calculate the third term using the same formula to see if it matches the third term of the sequence, which is 1313. \newlinea3=5a2+3=5(2)+3=10+3=13.a_{3}=-5a_{2}+3 = -5*(-2)+3 = 10+3 = 13.\newlineThis matches the third term of the given sequence, so this recursive formula is correct.

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