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Given the functions [tex]$f(n)=11$[/tex] and [tex]$g(n)=-2(n-1)$[/tex], combine them to create an arithmetic sequence, [tex]a_n[/tex], and solve for the 31st term.

A. [tex]a_n=11-2(n-1) \quad ; \quad a_{31}=-49[/tex]
B. [tex]a_n=11-2(n-1) \quad ; \quad a_{31}=-51[/tex]
C. [tex]a_n=11+2(n-1) \quad ; \quad a_{31}=71[/tex]
D. [tex]a_n=11+2(n-1) \quad ; \quad a_{31}=73[/tex]


Sagot :

To solve for the 31st term in the arithmetic sequence given by [tex]\( a_n = 11 - 2(n - 1) \)[/tex]:

1. Identify the general form of the sequence: We are given that the arithmetic sequence is described by the formula [tex]\( a_n = 11 - 2(n - 1) \)[/tex].

2. Plug in [tex]\( n = 31 \)[/tex] into the formula to find [tex]\( a_{31} \)[/tex]:

[tex]\[ a_{31} = 11 - 2(31 - 1) \][/tex]

3. Simplify the expression inside the parentheses:

[tex]\[ 31 - 1 = 30 \][/tex]

4. Multiply by -2:

[tex]\[ -2 \times 30 = -60 \][/tex]

5. Add the result to 11:

[tex]\[ 11 + (-60) = 11 - 60 = -49 \][/tex]

Therefore, the 31st term of the sequence, [tex]\( a_{31} \)[/tex], is [tex]\( -49 \)[/tex].

Thus, the correct solution is:
- [tex]\( a_n = 11 - 2(n - 1) ; a_{31} = -49 \)[/tex]