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What is the sum of the geometric sequence -4, 24, -144, ... if there are 8 terms?
Solution:
The formula to find the sum of geometric sequence is a(rn - 1)/(r - 1)
Where a is the first number, r is the common ratio, and n is the number of terms
It is given that geometric sequence -4, 24, -144,...8 terms
⇒ a = -4
⇒ r = 24/-4 = -6
⇒ n = 8
Substituting it in the formula, we get
Sum of the geometric sequence = a(rn - 1)/(r - 1)
= -4(-68 - 1)/(-6 - 1)
By further calculation
= -4(1679616 - 1)/ -7
= -4 (1679615)/-7
So we get,
= 6718460/7
= 959780
Therefore, the sum of the geometric sequence is 959780.
What is the sum of the geometric sequence -4, 24, -144, ... if there are 8 terms?
Summary:
The sum of the geometric sequence -4, 24, -144, ... if there are 8 terms is 959780.
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