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Find the sum of the first 10 terms of the following sequence. Round to the nearest hundredth if necessary.

4,quad-10,quad25,dots
Sum of a finite geometric series:

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

Find the sum of the first 1010 terms of the following sequence. Round to the nearest hundredth if necessary.\newline4,10,25, 4, \quad-10, \quad 25, \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 1010 terms of the following sequence. Round to the nearest hundredth if necessary.\newline4,10,25, 4, \quad-10, \quad 25, \ldots \newlineSum of a finite geometric series:\newlineSn=a1a1rn1r S_{n}=\frac{a_{1}-a_{1} r^{n}}{1-r} \newlineAnswer:
  1. Identify Pattern: First, we need to identify the pattern of the sequence to determine if it's arithmetic, geometric, or neither. By examining the given terms, we can see that each term is multiplied by a common ratio to get the next term: 10-10 is 2.5-2.5 times 44, and 2525 is 2.5-2.5 times 10-10. This indicates that the sequence is geometric with a common ratio of 2.5-2.5.
  2. Find Sum Formula: Next, we need to find the sum of the first 1010 terms of this geometric sequence. We can use the formula for the sum of the first nn terms of a geometric series, which is:\newlineSn=a1a1rn1rS_n = \frac{a_1 - a_1 \cdot r^n}{1 - r}\newlinewhere SnS_n is the sum of the first nn terms, a1a_1 is the first term, rr is the common ratio, and nn is the number of terms.
  3. Plug in Values: Now, let's plug in the values we know into the formula. The first term a1a_1 is 44, the common ratio rr is 2.5-2.5, and the number of terms nn is 1010.\newlineS10=44×(2.5)101(2.5)S_{10} = \frac{4 - 4 \times (-2.5)^{10}}{1 - (-2.5)}
  4. Calculate Numerator: We calculate the numerator and the denominator separately. First, we calculate 4×(2.5)104 \times (-2.5)^{10}:\newline4×(2.5)10=4×9536.74316406254 \times (-2.5)^{10} = 4 \times 9536.7431640625 (rounded to the nearest hundredth)
  5. Calculate Denominator: Now we calculate the denominator:\newline1(2.5)=1+2.5=3.51 - (-2.5) = 1 + 2.5 = 3.5
  6. Substitute Values: We substitute these values back into the formula to find S10S_{10}:\newlineS10=(438146.97265625)/3.5S_{10} = (4 - 38146.97265625) / 3.5
  7. Perform Subtraction: Now we perform the subtraction in the numerator:\newline438146.97265625=38142.972656254 - 38146.97265625 = -38142.97265625
  8. Divide Numerator: Finally, we divide the numerator by the denominator to find S10S_{10}:\newlineS10=38142.97265625/3.5S_{10} = -38142.97265625 / 3.5
  9. Perform Division: Performing the division gives us:\newlineS1010900.85S_{10} \approx -10900.85 (rounded to the nearest hundredth)

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