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Find the sum of the first 7 terms of the following sequence. Round to the nearest hundredth if necessary.

8,quad24,quad72,dots
Sum of a finite geometric series:

S_(n)=(a_(1)-a_(1)r^(n))/(1-r)
Answer:

Find the sum of the first 77 terms of the following sequence. Round to the nearest hundredth if necessary.\newline8,24,72, 8, \quad 24, \quad 72, \ldots \newlineSum of a finite geometric series:\newlineSn=a1a1rn1r S_{n}=\frac{a_{1}-a_{1} r^{n}}{1-r} \newlineAnswer:

Full solution

Q. Find the sum of the first 77 terms of the following sequence. Round to the nearest hundredth if necessary.\newline8,24,72, 8, \quad 24, \quad 72, \ldots \newlineSum of a finite geometric series:\newlineSn=a1a1rn1r S_{n}=\frac{a_{1}-a_{1} r^{n}}{1-r} \newlineAnswer:
  1. Identify type of sequence: Identify the type of sequence.\newlineThe given sequence is 8,24,72,8, 24, 72, \ldots, which is a geometric sequence because each term after the first is found by multiplying the previous term by a constant ratio.
  2. Determine common ratio: Determine the common ratio rr of the sequence.\newlineTo find the common ratio, divide the second term by the first term.\newliner=248=3r = \frac{24}{8} = 3
  3. Use formula for sum: Use the formula for the sum of the first nn terms of a geometric series.\newlineThe formula for the sum of the first nn terms (SnS_n) of a geometric series is:\newlineSn=a1a1rn1rS_n = \frac{a_1 - a_1 \cdot r^n}{1 - r}\newlinewhere a1a_1 is the first term and rr is the common ratio.
  4. Plug values into formula: Plug the values into the formula to find the sum of the first 77 terms.a1=8a_1 = 8 (the first term)r=3r = 3 (the common ratio)n=7n = 7 (the number of terms to sum)S7=88×3713S_7 = \frac{8 - 8 \times 3^7}{1 - 3}
  5. Calculate sum: Calculate the sum using the values from Step 44.\newlineS7=(88×37)(13)S_7 = \frac{(8 - 8 \times 3^7)}{(1 - 3)}\newlineS7=(88×2187)(2)S_7 = \frac{(8 - 8 \times 2187)}{(-2)}\newlineS7=(817496)(2)S_7 = \frac{(8 - 17496)}{(-2)}\newlineS7=(17488)(2)S_7 = \frac{(-17488)}{(-2)}\newlineS7=8744S_7 = 8744

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