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OverLord2011 [107]
3 years ago
8

X2 - 7x + 9 =0 please leave answer in surf form and simplify ​

Mathematics
2 answers:
scZoUnD [109]3 years ago
8 0

Answer:

Using quadratic formula again :)

777dan777 [17]3 years ago
4 0

Answer:

x = \frac{7}{2} ± \frac{\sqrt{13} }{2}

Step-by-step explanation:

Given

x² - 7x + 9 = 0 ( subtract 9 from both sides )

x² - 7x = - 9

Solve using the method of completing the square

add ( half the coefficient of the x- term)² to both sides

x² + 2( - \frac{7}{2} )x + \frac{49}{4} = - 9 +

(x - \frac{7}{2} )² = \frac{13}{4} ( take the square root of both sides )

x - \frac{7}{2} = ± \sqrt{\frac{13}{4} } = ± \frac{\sqrt{13} }{2} ( add

x = \frac{7}{2} ± \frac{\sqrt{13} }{2} = \frac{7+/-\sqrt{13} }{2}

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An experiment to investigate the survival time in hours of an electronic component consists of placing the parts in a test cell
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Answer:

a) The sample mean is of 49 and the sample standard deviation is of 11.7.

b) The range of the true mean at 90% confidence level is of 9.62 hours.

c) The prediction interval, at a 90% confidence level, of it's failure time is between 39.38 hours and 58.62 hours.

Step-by-step explanation:

Question a:

Sample mean:

\overline{x} = \frac{34+40+46+49+61+64}{6} = 49

Sample standard deviation:

s = sqrt{\frac{(34-49)^2+(40-49)^2+(46-49)^2+(49-49)^2+(61-49)^2+(64-49)^2}{5}} = 11.7

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b)Determine the range of the true mean at 90% confidence level.

We have to find the margin of error of the confidence interval. Since we have the standard deviation for the sample, the t-distribution is used.

The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So

df = 6 - 1 = 5

90% confidence interval

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M = T\frac{s}{\sqrt{n}}

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(c)If a seventh sample is tested, what is the prediction interval (90% confidence level) of its failure time.

This is the confidence interval, so:

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The upper end of the interval is the sample mean added to M. So it is 49 + 9.62 = 58.62 hours.

The prediction interval, at a 90% confidence level, of it's failure time is between 39.38 hours and 58.62 hours.

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Answer:

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Step-by-step explanation:

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