Q. Find the sum of the infinite geometric series.−10−5−25−45+⋯Write your answer as an integer or a fraction in simplest form.
Identify the first term: Identify the first term a1 of the geometric series.The first term a1 is the first number in the series, which is −10.
Determine the common ratio: Determine the common ratio r of the geometric series.The common ratio r can be found by dividing the second term by the first term: r=a1a2=−10−5=21.
Use the formula for the sum: Use the formula for the sum of an infinite geometric series.The formula is S=1−ra1, where S is the sum, a1 is the first term, and r is the common ratio.
Plug the values into the formula: Plug the values of a1 and r into the formula to find the sum.S=1−(21)−10=21−10=(−10)⋅12=−20.
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