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Which recursive sequence would produce the sequence 
4,-22,108,dots ?

a_(1)=4 and 
a_(n)=2a_(n-1)-6

a_(1)=4 and 
a_(n)=-2a_(n-1)-5

a_(1)=4 and 
a_(n)=-6a_(n-1)+2

a_(1)=4 and 
a_(n)=-5a_(n-1)-2

Which recursive sequence would produce the sequence 4,22,108, 4,-22,108, \ldots ?\newlinea1=4 a_{1}=4 and an=2an16 a_{n}=2 a_{n-1}-6 \newlinea1=4 a_{1}=4 and an=2an15 a_{n}=-2 a_{n-1}-5 \newlinea1=4 a_{1}=4 and an=6an1+2 a_{n}=-6 a_{n-1}+2 \newlinea1=4 a_{1}=4 and an=5an12 a_{n}=-5 a_{n-1}-2

Full solution

Q. Which recursive sequence would produce the sequence 4,22,108, 4,-22,108, \ldots ?\newlinea1=4 a_{1}=4 and an=2an16 a_{n}=2 a_{n-1}-6 \newlinea1=4 a_{1}=4 and an=2an15 a_{n}=-2 a_{n-1}-5 \newlinea1=4 a_{1}=4 and an=6an1+2 a_{n}=-6 a_{n-1}+2 \newlinea1=4 a_{1}=4 and an=5an12 a_{n}=-5 a_{n-1}-2
  1. Test Recursive Sequence 11: Let's test each recursive sequence by applying the given formulas to the initial term a1=4a_{1}=4 and see which one produces the sequence 4,22,108,4, -22, 108, \ldots.\newlineFirst, we'll test the recursive sequence a1=4a_{1}=4 and an=2an16a_{n}=2a_{n-1}-6.\newlinea2=2a16=2×46=86=2a_{2} = 2a_{1} - 6 = 2\times4 - 6 = 8 - 6 = 2\newlineThis does not match the second term of the sequence, which is 22-22.
  2. Test Recursive Sequence 22: Now, let's test the recursive sequence a1=4a_{1}=4 and an=2an15a_{n}=-2a_{n-1}-5. a2=2a15=2×45=85=13a_{2} = -2a_{1} - 5 = -2\times4 - 5 = -8 - 5 = -13 This does not match the second term of the sequence, which is 22-22.
  3. Test Recursive Sequence 33: Next, we'll test the recursive sequence a1=4a_{1}=4 and an=6an1+2a_{n}=-6a_{n-1}+2. a2=6a1+2=6×4+2=24+2=22a_{2} = -6a_{1} + 2 = -6\times4 + 2 = -24 + 2 = -22 This matches the second term of the sequence. Let's find the third term to see if the pattern continues. a3=6a2+2=6×(22)+2=132+2=134a_{3} = -6a_{2} + 2 = -6\times(-22) + 2 = 132 + 2 = 134 This does not match the third term of the sequence, which is 108108.
  4. Test Recursive Sequence 44: Finally, let's test the recursive sequence a1=4a_{1}=4 and an=5an12a_{n}=-5a_{n-1}-2. a2=5a12=5×42=202=22a_{2} = -5a_{1} - 2 = -5\times4 - 2 = -20 - 2 = -22 This matches the second term of the sequence. Let's find the third term to see if the pattern continues. a3=5a22=5×(22)2=1102=108a_{3} = -5a_{2} - 2 = -5\times(-22) - 2 = 110 - 2 = 108 This matches the third term of the sequence. Therefore, this recursive sequence produces the given sequence.

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