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{[f(1)=-8],[f(n)=f(n-1)-3]:}
Find an explicit formula for 
f(n).

f(n)=

{f(1)=8f(n)=f(n1)3 \left\{\begin{array}{l} f(1)=-8 \\ f(n)=f(n-1)-3 \end{array}\right. \newlineFind an explicit formula for f(n) f(n) .\newlinef(n)= f(n)=

Full solution

Q. {f(1)=8f(n)=f(n1)3 \left\{\begin{array}{l} f(1)=-8 \\ f(n)=f(n-1)-3 \end{array}\right. \newlineFind an explicit formula for f(n) f(n) .\newlinef(n)= f(n)=
  1. Identify sequence type: Identify the type of sequence described by the function f(n)f(n). The function f(n)=f(n1)3f(n) = f(n-1) - 3 suggests that this is an arithmetic sequence because the difference between consecutive terms is constant.
  2. Determine first term: Determine the first term of the sequence. We are given that f(1)=8f(1) = -8, so the first term, a1a_1, is 8-8.
  3. Find common difference: Determine the common difference of the sequence. The function f(n)=f(n1)3f(n) = f(n-1) - 3 indicates that the common difference, dd, is 3-3 because each term is 33 less than the previous term.
  4. Use explicit formula: Use the explicit formula for an arithmetic sequence, which is an=a1+(n1)da_n = a_1 + (n-1)d. Substitute the values of a1a_1 and dd into the formula. In this case, a1=8a_1 = -8 and d=3d = -3.
  5. Write formula for sequence: Write the explicit formula for the sequence using the values from Step 44. The formula is f(n)=8+(n1)(3)f(n) = -8 + (n-1)(-3).
  6. Simplify the formula: Simplify the formula. f(n)=83(n1)=83n+3=3n5f(n) = -8 - 3(n-1) = -8 - 3n + 3 = -3n - 5.

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