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

a_(1)=4" and "a_(n)=a_(n-1)+5
Answer: 
a_(n)=

Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=4 and an=an1+5 a_{1}=4 \text { and } a_{n}=a_{n-1}+5 \newlineAnswer: an= a_{n}=

Full solution

Q. Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=4 and an=an1+5 a_{1}=4 \text { and } a_{n}=a_{n-1}+5 \newlineAnswer: an= a_{n}=
  1. Identify Pattern: To find the explicit formula for the sequence, we need to determine a pattern that can be applied directly to find any term in the sequence without having to find all the previous terms.
  2. Find First Terms: Let's start by finding the first few terms of the sequence using the recursive formula:\newlinea1=4a_{1} = 4 (given)\newlinea2=a1+5=4+5=9a_{2} = a_{1} + 5 = 4 + 5 = 9\newlinea3=a2+5=9+5=14a_{3} = a_{2} + 5 = 9 + 5 = 14\newlinea4=a3+5=14+5=19a_{4} = a_{3} + 5 = 14 + 5 = 19\newlineFrom this pattern, we can see that each term is 55 more than the previous term.
  3. Analyze Relationship: Now, let's look at the relationship between the term number nn and the value of each term: a1=4=4+5(11)a_{1} = 4 = 4 + 5(1 - 1) a2=9=4+5(21)a_{2} = 9 = 4 + 5(2 - 1) a3=14=4+5(31)a_{3} = 14 = 4 + 5(3 - 1) a4=19=4+5(41)a_{4} = 19 = 4 + 5(4 - 1) We can see that the term value is equal to the first term 44 plus 55 times (n1)(n - 1).
  4. Determine Explicit Formula: The pattern suggests that the explicit formula for the nnth term is:\newlinean=4+5(n1)a_{n} = 4 + 5(n - 1)\newlineThis formula allows us to calculate the value of any term directly.
  5. Verify Formula: To verify that this formula is correct, let's test it with n=5n = 5:
    a5=4+5(51)=4+5(4)=4+20=24a_{5} = 4 + 5(5 - 1) = 4 + 5(4) = 4 + 20 = 24
    Now, let's check it with the recursive definition:
    a5=a4+5=19+5=24a_{5} = a_{4} + 5 = 19 + 5 = 24
    Both methods give us the same result, confirming that our explicit formula is correct.

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