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3 years ago

−5x+2y=9 y=7x x= y=

Mathematics

1 answer:

Serhud [2]3 years ago

4 0

$- 5x+2y=9 \\ y=7x$

We know that y=7x, so we just need tu put it into the 1st equation

$- 5x + 2 \times 7x = 9 \\ - 5x + 14x = 9 \\ 9x = 9 | \div 9 \\ 9x \div 9 = 9 \div 9 \\ x = 1$

So we found x. Now we can find y

$y = 7 \times 1 \\ y = 7$

Answer:

x=1, y=7; or (1;7)

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Answer:

The 99% confidence interval is given by ($144.677;$155.323)

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1) Notation and definitions

n=60 represent the sample size

$\bar X= 150$ represent the sample mean

$s=15.5$ represent the sample standard deviation

m represent the margin of error

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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".

2) Calculate the critical value tc

In order to find the critical value is important to mention that we don't know about the population standard deviation, so on this case we need to use the t distribution. Since our interval is at 99% of confidence, our significance level would be given by $\alpha=1-0.99=0.01$ and $\alpha/2 =0.005$ . The degrees of freedom are given by: