Find the sum of the first 10 terms of the following sequence. Round to the nearest hundredth if necessary.4,−10,25,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
Q. Find the sum of the first 10 terms of the following sequence. Round to the nearest hundredth if necessary.4,−10,25,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
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 is −2.5 times 4, and 25 is −2.5 times −10. This indicates that the sequence is geometric with a common ratio of −2.5.
Find Sum Formula: Next, we need to find the sum of the first 10 terms of this geometric sequence. We can use the formula for the sum of the first n terms of a geometric series, which is:Sn=1−ra1−a1⋅rnwhere Sn is the sum of the first n terms, a1 is the first term, r is the common ratio, and n is the number of terms.
Plug in Values: Now, let's plug in the values we know into the formula. The first term a1 is 4, the common ratio r is −2.5, and the number of terms n is 10.S10=1−(−2.5)4−4×(−2.5)10
Calculate Numerator: We calculate the numerator and the denominator separately. First, we calculate 4×(−2.5)10:4×(−2.5)10=4×9536.7431640625 (rounded to the nearest hundredth)
Calculate Denominator: Now we calculate the denominator:1−(−2.5)=1+2.5=3.5
Substitute Values: We substitute these values back into the formula to find S10:S10=(4−38146.97265625)/3.5
Perform Subtraction: Now we perform the subtraction in the numerator:4−38146.97265625=−38142.97265625
Divide Numerator: Finally, we divide the numerator by the denominator to find S10:S10=−38142.97265625/3.5
Perform Division: Performing the division gives us:S10≈−10900.85 (rounded to the nearest hundredth)
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