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zavuch27 [327]
3 years ago
9

Will mark brainliest!!

Mathematics
1 answer:
wlad13 [49]3 years ago
7 0
<span>Solve the system

9x = 27-9y
20x=71-9y

Let's use the "elimination through addition/subtraction method.
Multiply the first equation by -1 so as to obtain +9y:

-9x = -27 + 9y
</span><span>20x=  71-   9y
--------------------

Add these 2 equations together:

</span>-9x = -27 + 9y
20x=  71-   9y
--------------------
<span> 11x = 44

Solve this for x:  x = 44/11 = 4.

Now find y by subst. 4 for x in either of the original equations.

Using the second equation:    </span><span> 

</span>20x=71-9y
20(4) = 71 - 9y
80-71 = -9y
9 = -9y.  Then y = -1.

The solution set is (4,-1).
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(-5/2,-4)

Step-by-step explanation:

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The 2008 Workplace Productivity Survey, commissioned by LexisNexis and prepared by World One Research, included the question, "H
LenaWriter [7]

Answer:

A 95% confidence interval estimate of the mean number of hours a legal professional works on a typical workday is [7.44 hours, 10.56 hours].

Step-by-step explanation:

We are given that x is normally distributed with a known standard deviation of 12.6.

A sample of 250 legal professionals was surveyed, and the sample's mean response was 9 hours.

Firstly, the pivotal quantity for finding the confidence interval for the population mean is given by;

                               P.Q.  =  \frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }  ~ N(0,1)

where, \bar X = sample average mean response = 9 hours

            \sigma  = population standard deviation = 12.6

            n = sample of legal professionals = 250

            \mu = mean number of hours a legal professional works

<em>Here for constructing a 95% confidence interval we have used One-sample z-test statistics as we know about population standard deviation.</em>

<u>So, 95% confidence interval for the population mean, </u>\mu<u> is ;</u>

P(-1.96 < N(0,1) < 1.96) = 0.95  {As the critical value of z at 2.5% level

                                                   of significance are -1.96 & 1.96}  

P(-1.96 < \frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } } < 1.96) = 0.95

P( -1.96 \times {\frac{\sigma}{\sqrt{n} } } < {\bar X-\mu} < -1.96 \times {\frac{\sigma}{\sqrt{n} } } ) = 0.95

P( \bar X-1.96 \times {\frac{\sigma}{\sqrt{n} } } < \mu < \bar X+1.96 \times {\frac{\sigma}{\sqrt{n} } } ) = 0.95

<u>95% confidence interval for</u> \mu = [ \bar X-1.96 \times {\frac{\sigma}{\sqrt{n} } } , \bar X+1.96 \times {\frac{\sigma}{\sqrt{n} } } ]

                                       = [ 9-1.96 \times {\frac{12.6}{\sqrt{250} } } , 9+1.96 \times {\frac{12.6}{\sqrt{250} } } ]

                                       = [7.44 hours, 10.56 hours]

Therefore, a 95% confidence interval estimate of the mean number of hours a legal professional works on a typical workday is [7.44 hours, 10.56 hours].

5 0
3 years ago
How to simply this radical
kondor19780726 [428]
16✔️75
16✔️25 • 3
16 • 5 • ✔️3
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The radical can be simplified to 80✔️3.
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