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The explicit rule for a sequence is an=9(−5)n−1 .



What is recursive rule for the sequence?




an=5−(an−1),a1=9

an=−9(an−1),a1=5

an=9−(an−1),a1=5

an=−5(an−1),a1=9

Respuesta :

Explicit rule is a(n) = 9*(-5)^(n-1)

The recursive rule is a(n) = -5*a(n-1); a(1) = 9

The first term is 9. Each new term is found by multiplying the previous term by -5

We can see this when we raise -5 to a whole number power. Eg: 9(-5)^3 = 9*(-5)*(-5)*(-5)

Answer: Choice D

Answer:

Option 4th is correct.

[tex]a_n = -5 \cdot a_{n-1}[/tex] , [tex]a_1 = 9[/tex]

Step-by-step explanation

The explicit sequence of the geometric sequence is given by:

[tex]a_n = a_1r^{n-1}[/tex]              ....[1]

where,

r is the common ratio

n is the number of terms

[tex]a_1[/tex] is the first term

As per the statement:

The explicit rule for a sequence is:

[tex]a_n=9(-5)^{n-1}[/tex]

On comparing [1] we have;

[tex]a_1 = 9[/tex] and r=  -5

Recursive formula for the geometric sequence is given by:

[tex]a_n = r \cdot a_{n-1}[/tex]  for [tex]n\geq 2[/tex]

Substitute the given values we have;

[tex]a_n = -5 \cdot a_{n-1}[/tex]

Therefore, the recursive rule for the sequence is, [tex]a_n = -5 \cdot a_{n-1}[/tex] , [tex]a_1 = 9[/tex]