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What is the 7th term of the geometric sequence where a1 = -625 and a2 = 125?
What is the 7th term of the geometric sequence where a1 = -625 and a2 = 125? (1 points)
A) -0.2
B) 0.04
C) -0.04
D) 0.2
What is the sum of the geometric sequence -1, 6, -36, … if there are 6 terms? (1 points)
A) -39,991
B) 6,665
C) -6,665
D) 39,991
What is the sum of a 7-term geometric series if the first term is -6, the last term is -24,576, and the common ratio is -4? (1 points)
A) -32,766
B) -19,662
C) 19,662
D) 32,766
2 Answers
- kellenraidLv 69 years agoFavorite Answer
What is 7th term? Answer B) 0.04
Formula for the nth term is
an = a r^(n-1)
where the scale = a = first term = 625
and r = ration of any two consequetive terms = 125/(-625) = - 0.04
so that a7 = -625(-1/5)^(7-1) = -0.04
What is the sum...?
a = -6
r = 6/(-1) = -6
SUM|k=1 to n=6| = a(1-r^(n+1))/(1-r) = (-6)(1-(-6)^(6+1))/(1--6)
What is sum...?
a = -6
Last term = -24,576
r = -4
Use the SUM formula above and you are home in time for ice cream
Source(s): Wikipedia: geometric sequences - Anonymous4 years ago
a1 = 625 a2 = -a hundred twenty five 625/-a hundred twenty five = -5 is the sequence.. a3 = -a hundred twenty five/-5 = 25 a4 = 25/-5 = -5 a5 = -5/-5 = a million a6 = a million/-5 = -a million/5 a7 = (-a million/5) / -5 = (-a million/5) * (-a million/5) ---> (flipped fraction whilst multiplying) = a million/25 hence, the seventh term of the geometric sequence is a million/25 desire that facilitates.