Find the sum of the first 7 terms of the following sequence. Round to the nearest hundredth if necessary.8,24,72,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
Q. Find the sum of the first 7 terms of the following sequence. Round to the nearest hundredth if necessary.8,24,72,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
Identify type of sequence: Identify the type of sequence.The given sequence is 8,24,72,…, which is a geometric sequence because each term after the first is found by multiplying the previous term by a constant ratio.
Determine common ratio: Determine the common ratio r of the sequence.To find the common ratio, divide the second term by the first term.r=824=3
Use formula for sum: Use the formula for the sum of the first n terms of a geometric series.The formula for the sum of the first n terms (Sn) of a geometric series is:Sn=1−ra1−a1⋅rnwhere a1 is the first term and r is the common ratio.
Plug values into formula: Plug the values into the formula to find the sum of the first 7 terms.a1=8 (the first term)r=3 (the common ratio)n=7 (the number of terms to sum)S7=1−38−8×37
Calculate sum: Calculate the sum using the values from Step 4.S7=(1−3)(8−8×37)S7=(−2)(8−8×2187)S7=(−2)(8−17496)S7=(−2)(−17488)S7=8744
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