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3 years ago

Find the sum of a finite geometric sequence from n = 1 to n = 7, using the expression −4(6)n − 1.

Mathematics

1 answer:

Verizon [17]3 years ago

7 0

Answer:

Step-by-step explanation:

The formula of a sum of terms of a gometric sequence:

$S_n=a_1\cdot\dfrac{1-r^n}{1-r}$

a₁ - first term

r - common ratio

We have

$a_n=-4(6)^{n-1}$

Calculate a₁. Put n = 1:

$a_1=-4(6)^{1-1}=-4(6)^0=-4(1)=-4$

Calculate the common ratio:

$r=\dfrac{a_{n+1}}{a_n}\\\\a_{n+1}=-4(6)^{n+1-1}=-4(6)^n\\\\r=\dfrac{-4(6)^n}{-4(6)^{n-1}}=6^n:6^{n-1}\\\\\text{use}\ a^n:a^m=a^{n-m}\\\\r=6^{n-(n-1)}=6^{n-n+1}=6^1=6$

$\text{Substitute}\ a_1=-4,\ n=7,\ r=6:\\\\S_7=-4\cdot\dfrac{1-6^7}{1-6}=-4\cdot\dfrac{1-279936}{-5}=-4\cdot\dfrac{-279935}{-5}=(-4)(55987)\\\\S_7=-223948$

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Nolan and his children went into a grocery store and he bought $8 worth of apples

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Nolan and his children bought fruits (Apples and bananas) worth $8.

Cost of each apple and bananas are $2 and $0.40 respectively.

Let the number of bananas he bought = y

And the number of apples = x

Therefore, cost of the apples =$2x

And the cost of bananas = $0.40y

Total cost of 'x' apples and 'y' bananas = $(2x + 0.40y)

Equation representing the total cost of fruits will be,

(2x + 0.40y) = 8

10(2x + 0.40y) = 10(8)

20x + 4y = 80

5x + y = 20 --------(1)

If he bought 5 times as many bananas as apples,

y = 5x ------(2)

Substitute the value of y from equation (2) to equation (1),

5x + 5x = 20

10x = 20

x = 2

Substitute the value of 'x' in equation (2)

y = 5(2)

y = 10

Therefore, Nolan bought 2 apples and 10 bananas.

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2 years ago

What is the value of a1 of the geometric series? Sigma-Summation Underscript n = 1 Overscript infinity EndScripts 12 (negative o

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Answer:

Step-by-step explanation:

The given geometric series is

$\sum_{n = 1}^{ \infty} 12( { - \frac{1}{9} })^{n - 1}$

We want to determine the first term of this geometric series.

Recall that the explicit formula is

$a_{n} = 12( { - \frac{1}{9} })^{n - 1}$

To find the first term, we put n=1 to get:

$a_{1} = 12( { - \frac{1}{9} })^{1 - 1}$

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According to the Vivino website, suppose the mean price for a bottle of red wine that scores 4.0 or higher on the Vivino Rating

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Answer:

a) Null and alternative hypothesis

$H_0: \mu=32.48\\\\H_a:\mu< 32.48$

b) Test statistic t=-1.565

P-value = 0.0612

NOTE: the sample size is n=65.

c) Do not reject H0. We cannot conclude that the price in Providence for a bottle of red wine that scores 4.0 or higher on the Vivino Rating System is less than the population mean of $32.48.

d) Null and alternative hypothesis

$H_0: \mu=32.48\\\\H_a:\mu< 32.48$

Test statistic t=-1.565

Critical value tc=-1.669

t>tc --> Do not reject H0

Do not reject H0. We cannot conclude that the price in Providence for a bottle of red wine that scores 4.0 or higher on the Vivino Rating System is less than the population mean of $32.48.

Step-by-step explanation:

This is a hypothesis test for the population mean.

The claim is that the mean price in Providence for a bottle of red wine that scores 4.0 or higher on the Vivino Rating System is less than the population mean of $32.48.

Then, the null and alternative hypothesis are:

$H_0: \mu=32.48\\\\H_a:\mu< 32.48$

The significance level is 0.05.

The sample has a size n=65.

The sample mean is M=30.15.

As the standard deviation of the population is not known, we estimate it with the sample standard deviation, that has a value of s=12.

The estimated standard error of the mean is computed using the formula:

$s_M=\dfrac{s}{\sqrt{n}}=\dfrac{12}{\sqrt{65}}=1.4884$

Then, we can calculate the t-statistic as:

$t=\dfrac{M-\mu}{s/\sqrt{n}}=\dfrac{30.15-32.48}{1.4884}=\dfrac{-2.33}{1.4884}=-1.565$

The degrees of freedom for this sample size are:

$df=n-1=65-1=64$

This test is a left-tailed test, with 64 degrees of freedom and t=-1.565, so the P-value for this test is calculated as (using a t-table):

$\text{P-value}=P(t$

As the P-value (0.0612) is bigger than the significance level (0.05), the effect is not significant.

The null hypothesis failed to be rejected.

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<u>Critical value approach</u>

<u></u>

At a significance level of 0.05, for a left-tailed test, with 64 degrees of freedom, the critical value is t=-1.669.

As the test statistic is greater than the critical value, it falls in the acceptance region.

The null hypothesis failed to be rejected.

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Step-by-step explanation:

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