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3 years ago

If x^2+y^2=49,xy=7 find x^3-y^3

Mathematics

1 answer:

Vikki [24]3 years ago

4 0

Answer: 0

Step-by-step explanation: First substitute 7 for x and y

7^3-7^3 = 0

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In a survey, the planning value for the population proportion is p* = 0.35. How large a sample should be taken to provide a 95%

lions [1.4K]

Answer:

$n=\frac{0.35(1-0.35)}{(\frac{0.05}{1.96})^2}=349.59$

And rounded up we have that n=350

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

$p$ represent the real population proportion of interest

$\aht p$ represent the estimated proportion for the sample

n is the sample size required (variable of interest)

$z$ represent the critical value for the margin of error

Solution to the problem

The population proportion have the following distribution

$p \sim N(p,\sqrt{\frac{\hat p(1-\hat p)}{n}})$

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 95% of confidence, our significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$ . And the critical value would be given by:

$z_{\alpha/2}=-1.96, z_{1-\alpha/2}=1.96$

The margin of error for the proportion interval is given by this formula:

$ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}$ (a)

And on this case we have that $ME =\pm 0.05$ and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2}$ (b)

And replacing into equation (b) the values from part a we got:

$n=\frac{0.35(1-0.35)}{(\frac{0.05}{1.96})^2}=349.59$

And rounded up we have that n=350

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3 years ago

I need someone who will answer all five questions correctly. Give out 100 bonus points for who will answer all 5 correctly

KATRIN_1 [288]

Answer:

The circumference of the yellow circle is $9\pi$ or $28.27cm^2$ approximately, the circumference of the blue circle is $6\pi$ or $18.85m^2$ approximately, the circumference of the green circle is $80\pi$ or $251.33mm^2$ approximately, the circumference of the red circle is $5\pi$ or $15.71cm^2$ approximately, and the circumference of the pink circle is $7\pi$ or $21.99cm^2$ approximately.

Step-by-step explanation:

To find the circumference of a circle, you need to multiply the diameter of the circle and multiply it by $\pi$ . In this case, the circumferences of the yellow circle are $9\pi$ or approximately $28.27cm^2$ , the circumference of the blue circle is $6\pi$ or approximately $18.85m^2$ , the circumference of the green circle is $80\pi$ or approximately $251.33mm^2$ , the circumference of the red circle is $5\pi$ or approximately $15.71cm^2$ , and the circumference of the pink circle is $7\pi$ or approximately $21.99cm^2$ .

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