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Write the explicit formula for the arithmetic sequence below and use it to find the 52nd term: 25, 19, 13, 7

Sagot :

Answer:

[tex] \displaystyle \:a_n=- 6n + 31[/tex]

[tex] \displaystyle \:a_{52}= - 281[/tex]

Step-by-step explanation:

we are given some numbers

25,19,13,9

and said to figure out the sequence and 52 term

recall arithmetic sequence

[tex] \displaystyle \: a + (n - 1)d[/tex]

where a is the first term and d is the common difference

let's figure out d

[tex] \displaystyle \:d = 19 - 25 \\ d= - 6[/tex]

and a is 25

now we need to substitute the value of a and d and simplify to get our formula

substitute the value of a and d:

[tex] \displaystyle \: 25 + (n - 1) (- 6)[/tex]

distribute -6:

[tex] \displaystyle \: 25 + ( - 6n + 6)[/tex]

remove parentheses:

[tex] \displaystyle \: 25 - 6n + 6[/tex]

simplify addition:

[tex] \displaystyle \: - 6n + 31[/tex]

so our formula is -6n+31

remember here n means nth number term

we are said to figure out 52 number term

so

substitute the value of n:

[tex] \displaystyle \: - 6.52 + 31[/tex]

simplify multiplication:

[tex] \displaystyle \: - 312 + 31[/tex]

simplify addition:

[tex] \displaystyle \: - 281[/tex]