Bytelearn - cat image with glassesAI tutor

Welcome to Bytelearn!

Let’s check out your problem:

Write an explicit formula that represents the sequence defined by the following recursive formula:

a_(1)=1" and "a_(n)=-4a_(n-1)
Answer: 
a_(n)=

Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=1 and an=4an1 a_{1}=1 \text { and } a_{n}=-4 a_{n-1} \newlineAnswer: an= a_{n}=

Full solution

Q. Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=1 and an=4an1 a_{1}=1 \text { and } a_{n}=-4 a_{n-1} \newlineAnswer: an= a_{n}=
  1. Find Terms: To find the explicit formula for the sequence, we need to determine the pattern of the sequence based on the given recursive formula. Let's start by finding the first few terms of the sequence.\newlinea1=1a_{1} = 1 (given)\newlinea2=4a1=4(1)=4a_{2} = -4a_{1} = -4(1) = -4\newlinea3=4a2=4(4)=16a_{3} = -4a_{2} = -4(-4) = 16\newlinea4=4a3=4(16)=64a_{4} = -4a_{3} = -4(16) = -64\newlineWe can see that the sequence is alternating in sign and each term is 44 times the previous term in magnitude.
  2. Identify Pattern: Now, let's look for a pattern in the exponents of 44 for each term.\newlinea1=40a_{1} = 4^0 (since 40=14^0 = 1)\newlinea2=41a_{2} = -4^1\newlinea3=42a_{3} = 4^2\newlinea4=43a_{4} = -4^3\newlineWe can see that the exponent of 44 is one less than the term number and the sign alternates with each term.
  3. Sign Pattern: To account for the alternating sign, we can use (1)(-1) raised to a power that will alternate the sign for each term. We can use the term number minus 11 as the exponent for (1)(-1) to alternate the sign.\newlineSo, the pattern for the sign is (1)(n1)(-1)^{(n-1)}.
  4. Combine Patterns: Combining the pattern for the magnitude of 44 and the alternating sign, we can write the explicit formula for the sequence as:\newlinean=(1)n1×4n1a_{n} = (-1)^{n-1} \times 4^{n-1}\newlineThis formula will give us the nnth term of the sequence by plugging in the value of nn.

More problems from Convert an explicit formula to a recursive formula