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Which sequence is modeled by the graph below?


Which Sequence Is Modeled By The Graph Below class=

Sagot :

  • (2,9)
  • (3,3)
  • (4,1)

We can observe

  • 9/3=3
  • 3/3=1

Its a geometric progression having first term 9(3)=27 and common ratio as 1/3

So

The firmula is

  • a_n=27(1/3)^{n-1}

Option C

Answer:

[tex]a_n=27\left(\dfrac{1}{3}\right)^{n-1}[/tex]

Step-by-step explanation:

From inspection of the graph, the given points are:

  • (2, 9)
  • (3, 3)
  • (4, 1)

If we draw a line through the given points, the line is a curve rather than a straight line. If the line was a straight line, the graph would be modeled as an arithmetic sequence. Therefore, as the line is a curve, the given points are modeling a geometric sequence.

General form of a geometric sequence:

 [tex]a_n=ar^{n-1}[/tex]

where:

  • a is the first term
  • r is the common ratio
  • [tex]a_n[/tex] is the nth term

Rewrite the given points as terms of the sequence:

  • (2, 9)  ⇒  a₂ = 9
  • (3, 3)  ⇒  a₃ = 3
  • (4, 1)  ⇒  a₄ = 1

To find the common ratio r, divide consecutive terms:

[tex]\implies r=\dfrac{a_3}{a_2}=\dfrac{3}{9}=\dfrac{1}{3}[/tex]

Calculate the first term (a) by substituting the found value of r and the given values of one of the terms into the formula:

[tex]\implies a_2=9[/tex]

[tex]\implies a\left(\dfrac{1}{3}\right)^{2-1}=9[/tex]

[tex]\implies \dfrac{1}{3}a=9[/tex]

[tex]\implies a=27[/tex]

Substitute the found values of r and a into the general formula to create the sequence modeled by the graph:

[tex]a_n=27\left(\dfrac{1}{3}\right)^{n-1}[/tex]

Learn more about geometric sequences here:

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