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In an arithmetic sequence, the sum of the second and eighth terms is $5$, and the product of the fourth and fifth terms is also $5$. What is the $20$th term of this sequence?

Respuesta :

Answer:

10

Step-by-step explanation:

Let $a_n$ be the $n$th term of this sequence. We know $a_2 + a_8 = 5$, and that forces $a_5 = \dfrac 5 2$, the average of these terms.

Then $a_4a_5 = 5$ gives us $a_4 = 2$.

The common difference is $\dfrac 1 2$, and in general, $a_n = \dfrac n 2$.

Therefore the $20$th term is $\dfrac{20}{2} = \boxed{10}$.

The 20th term of the arithmetic sequence will be equal to [tex]T_{20}=10[/tex]

What is arthematic sequence?

Arthematic sequence is the type of the number series in which the difference between the first and the second term is always constant in the whole series.

Let [tex]$a_n$[/tex]  be the nth term of this sequence.

We know

[tex]$a_2 + a_8 = 5$[/tex], and that forces  [tex]$a_5 = \dfrac 5 2$[/tex],  the average of these terms.

Then [tex]$a_4a_5 = 5$[/tex] gives us   [tex]a_4 = 2$.[/tex]

The common difference is  [tex]\dfrac 1 2$,[/tex]and in general,  [tex]$a_n = \dfrac n 2$[/tex].

Therefore the 20th term is

[tex]T_{20}=$\dfrac{20}{2} = \boxed{10}$.[/tex]

Hence the 20th term of the arithmetic sequence will be equal to [tex]T_{20}=10[/tex]

To know more about arthematic sequence follow

https://brainly.com/question/6561461

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