Respuesta :
The explicit rule for the sequence using subscript notation is [tex]a_n=2000\times1.2^{n-1}[/tex] .
- Explicit expressions are always used to represent any term in a sequence without describing any other term in the sequence. The meaning of "explicit" is direct, something that can be found directly without knowing the other terms in the sequence.
- A term in a sequence can be uniquely represented by a single expression, an explicit expression.
- Geometric Sequence: [tex]a_n=ar^{n-1}[/tex], where 'a' is the first term and 'r' is the common ratio.
It is given that sequence is G.P
In G.P 2nd and 4th is given by
[tex]a_2=ar[/tex] ...(1) and [tex]a_4=ar^3[/tex] ...(2)
We have given [tex]a_2=2400 , a_4=3456[/tex]
Putting in equation (1) and (2) , we get
[tex]2400=ar[/tex] ...(3) and [tex]3456=ar^3[/tex] ...(4)
On dividing equation (3) by equation (4) , we get
[tex]\frac{2400}{3456} =\frac{ar}{ar^3} \\\\\\ 0.6944=\frac{1}{r^2}\\\\r^2=1.44 \\r=1.2[/tex]
First term will be given by
[tex]a_1=a_2 r^{1-2}\\\\a_1=2400r^{-1}\\\\a_1=\frac{2400}{1.2} \\\\a_1=2000[/tex]
Nth term is given by
[tex]a_n=a_1r^{n-1}\\a_n=2000\times1.2^{n-1}[/tex]
Learn more about sequence here :
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