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MArishka [77]
3 years ago
15

the common ratio of a geometric series is 3 and the sum of the first 8 terms is 3280. what is the first term of the series?

Mathematics
1 answer:
andrew11 [14]3 years ago
4 0

Answer: 1

Step-by-step explanation:

The formula for calculating the sum of a Geometric series if the common ratio is greater than 1 is given as :

S_{n} = \frac{a(r^{n}-1) }{r-1}

Where S_{n} is the sum of terms , a is the first term , r is the common ratio and n is the number of terms.

From the question:

S_{n} = 3280

a = ?

r = 3

n = 8

Substituting this into the formula , we have

3280 = \frac{a(3^{8}-1) }{3-1}

3280 = \frac{a(6561-1)}{2}

Multiply through by 2 , we have

6560 = a ( 6560)

divide through by 6560, we have

6560/6560 = a(6560)/6560

Therefore : a = 1

The first term of the series is thus 1

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ololo11 [35]

Answer:

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Step-by-step explanation:

Suppose that we have two equations:

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k*(A = B) ---> k*A = k*B

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And then we "add" them:

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Now we have the equations:

-x  - y = 11

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We want to add them in a given form that one of the variables cancels, so we can solve it for the other variable.

Then we can take the first equation:

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4*x - 5*y = 10

(here we can think that we multiplied the second equation by 1, then we have k = 4, and j = 1)

If we add them, we get:

(-4*x - 4*y) + (4*x - 5*y) = 10 + 44

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Now that we know the value of y, we can simply replace it in one of the two equations to get the value of x.

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x = -5, and y = -6

5 0
3 years ago
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lakkis [162]
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Answer:

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Step-by-step explanation:

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In square PORS, side PO is parallel to side SR, and side PS is parallel to side QR. The square is reflected across the y-axis an
DiKsa [7]

The square is reflected but the part Ellen sides would remain the same as the starting location.


Side PO would be parallel to side PS. INCORRECT


Side PQ would be parallel to side SR. CORRECT


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