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Find the sum of the first 30 terms in this geometric series:

-5-4-(16)/(5)dots
Choose 1 answer:
(A) 
-1.24*10^(20)
(B) -24.97
(c) -2.78
(D) -0.04

Find the sum of the first 3030 terms in this geometric series:\newline54165 -5-4-\frac{16}{5} \ldots \newlineChoose 11 answer:\newline(A) 1.241020 -1.24 \cdot 10^{20} \newline(B) 24-24.9797\newline(C) 2-2.7878\newline(D) 0-0.0404

Full solution

Q. Find the sum of the first 3030 terms in this geometric series:\newline54165 -5-4-\frac{16}{5} \ldots \newlineChoose 11 answer:\newline(A) 1.241020 -1.24 \cdot 10^{20} \newline(B) 24-24.9797\newline(C) 2-2.7878\newline(D) 0-0.0404
  1. Identify first term and common ratio: Identify the first term (a1a_1) and the common ratio (rr) of the geometric series.\newlineThe first term a1a_1 is 5-5.\newlineTo find the common ratio rr, we divide the second term by the first term.\newliner=45=45r = \frac{-4}{-5} = \frac{4}{5}
  2. Use sum formula for geometric series: Use the formula for the sum of the first nn terms of a geometric series: Sn=a1×(1rn)/(1r)S_n = a_1 \times (1 - r^n) / (1 - r), where nn is the number of terms.\newlineHere, n=30n = 30, a1=5a_1 = -5, and r=45r = \frac{4}{5}.
  3. Plug values and calculate sum: Plug the values into the formula and calculate the sum. \newlineS30=5×(1(45)30)/(145)S_{30} = -5 \times (1 - (\frac{4}{5})^{30}) / (1 - \frac{4}{5})
  4. Simplify denominator: Simplify the denominator 1451 - \frac{4}{5}. \newline145=151 - \frac{4}{5} = \frac{1}{5}
  5. Calculate (4/5)30(4/5)^{30}: Calculate (4/5)30(4/5)^{30}.\newlineThis is a very small number because 4/54/5 is less than 11 and raising it to the 30th30th power will make it much smaller.
  6. Substitute values into formula: Substitute the values into the formula. S30=5×(1(45)30)/(15)S_{30} = -5 \times \left(1 - \left(\frac{4}{5}\right)^{30}\right) / \left(\frac{1}{5}\right)
  7. Multiply by 55 to simplify: Multiply both numerator and denominator by 55 to simplify the fraction.S30=5×5×(1(45)30)S_{30} = -5 \times 5 \times \left(1 - \left(\frac{4}{5}\right)^{30}\right)
  8. Simplify the multiplication: Simplify the multiplication. S30=25×(1(45)30)S_{30} = -25 \times (1 - (\frac{4}{5})^{30})
  9. Approximate sum: Since (45)30(\frac{4}{5})^{30} is a very small number, we can approximate 1(45)301 - (\frac{4}{5})^{30} as being very close to 11.S3025×1S_{30} \approx -25 \times 1
  10. Calculate approximate sum: Calculate the approximate sum. S3025S_{30} \approx -25