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Which recursive sequence would produce the sequence 
1,-5,13,dots ?

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

a_(1)=1 and 
a_(n)=-2a_(n-1)-3

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

a_(1)=1 and 
a_(n)=-3a_(n-1)-2

Which recursive sequence would produce the sequence 1,5,13, 1,-5,13, \ldots ?\newlinea1=1 a_{1}=1 and an=an14 a_{n}=-a_{n-1}-4 \newlinea1=1 a_{1}=1 and an=2an13 a_{n}=-2 a_{n-1}-3 \newlinea1=1 a_{1}=1 and an=4an11 a_{n}=-4 a_{n-1}-1 \newlinea1=1 a_{1}=1 and an=3an12 a_{n}=-3 a_{n-1}-2

Full solution

Q. Which recursive sequence would produce the sequence 1,5,13, 1,-5,13, \ldots ?\newlinea1=1 a_{1}=1 and an=an14 a_{n}=-a_{n-1}-4 \newlinea1=1 a_{1}=1 and an=2an13 a_{n}=-2 a_{n-1}-3 \newlinea1=1 a_{1}=1 and an=4an11 a_{n}=-4 a_{n-1}-1 \newlinea1=1 a_{1}=1 and an=3an12 a_{n}=-3 a_{n-1}-2
  1. Test Option 11: Let's test the first option: a1=1a_{1}=1 and an=an14a_{n}=-a_{n-1}-4. We start with a1=1a_{1}=1. To find a2a_{2}, we use the recursive formula: a2=a14=14=5a_{2}=-a_{1}-4 = -1-4 = -5. Now, let's find a3a_{3}: a3=a24=(5)4=54=1a_{3}=-a_{2}-4 = -(-5)-4 = 5-4 = 1. This does not match the given sequence since the third term should be 1313, not 11.
  2. Test Option 22: Let's test the second option: a1=1a_{1}=1 and an=2an13a_{n}=-2a_{n-1}-3. We start with a1=1a_{1}=1. To find a2a_{2}, we use the recursive formula: a2=2a13=2×13=23=5a_{2}=-2a_{1}-3 = -2\times1-3 = -2-3 = -5. Now, let's find a3a_{3}: a3=2a23=2×(5)3=103=7a_{3}=-2a_{2}-3 = -2\times(-5)-3 = 10-3 = 7. This does not match the given sequence since the third term should be 1313, not 77.
  3. Test Option 33: Let's test the third option: a1=1a_{1}=1 and an=4an11a_{n}=-4a_{n-1}-1. We start with a1=1a_{1}=1. To find a2a_{2}, we use the recursive formula: a2=4a11=4×11=41=5a_{2}=-4a_{1}-1 = -4\times1-1 = -4-1 = -5. Now, let's find a3a_{3}: a3=4a21=4×(5)1=201=19a_{3}=-4a_{2}-1 = -4\times(-5)-1 = 20-1 = 19. This does not match the given sequence since the third term should be 1313, not 1919.
  4. Test Option 44: Let's test the fourth option: a1=1a_{1}=1 and an=3an12a_{n}=-3a_{n-1}-2. We start with a1=1a_{1}=1. To find a2a_{2}, we use the recursive formula: a2=3a12=3×12=32=5a_{2}=-3a_{1}-2 = -3\times1-2 = -3-2 = -5. Now, let's find a3a_{3}: a3=3a22=3×(5)2=152=13a_{3}=-3a_{2}-2 = -3\times(-5)-2 = 15-2 = 13. This matches the given sequence since the third term is indeed 1313.

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