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Orlov [11]
3 years ago
14

How do I solve this using elimination? 80x + 45y = 645 x + y = 12

Mathematics
2 answers:
amid [387]3 years ago
8 0
If you combine like terms and do them differently you will have 3 different answers
sergeinik [125]3 years ago
7 0
X + y = 12  / x (-45);
Then, -45x - 45y = -540;
We have 80x + 45y = 645 and
               -45x - 45y = -540
            ________________
                35x           = 105;
Finally, x = 105÷35;
x = 3;
y = 12 - 3;
y = 9;
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Answer:

16

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19-3 =16

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A researcher is concerned that graduate students get less than the recommended 8 hours of sleep a night. She selects a random sa
dsp73

Answer:

H0 : μ = 8

H1 : μ < 8

Test statistic = - 7.51

conclude that there is statistical significance that student at the school get less than 8 hours of sleep on average.

Step-by-step explanation:

The hypothesis :

H0 : μ = 8

H1 : μ < 8

The test statistic :

(xbar - μ) ÷ (s/√(n))

Sample data :

1.75, 2, 2.25, 2.25, 2.5, 3, 3.5, 3.5, 3.5, 3.75, 4, 4.25, 4.5, 4.5, 4.5, 4.75, 5.25, 5.5, 5.75, 5.75, 5.75, 6, 6, 6, 6.25, 6.25, 6.25, 6.5, 6.5, 6.5, 6.75, 7, 7, 7, 7.5, 7.5, 7.75, 8, 8.25, 8.25, 8.25, 8.5, 8.75, 9, 9

Using calculator :

Sample mean, xbar = 5.71666

Sample standard deviation, s = 2.04

The test statistic :

(5.7166 - 8) ÷ (2.04/√(45))

-2.28 / 0.3041052

= - 7.5085

= - 7.51

Degree of freedom = 45 - 1 = 44

Pvalue(-7.51, 44) = 0.00001

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4 0
3 years ago
Consider the two regression lines 3x+2y=26 and 6x+y=31, the regression coefficient of y on x is
Olin [163]

The regression lines 3x+2y=26 and 6x+y=31 are linear regressions

The mean values are 4 and 7 and the correlation coefficient between x and y is 0.25

The standard deviation of x is 2/13

The mean value and the correlation

We have the equations to be:

3x+2y=26 and 6x+y=31

Make y the subject in the second equation

y = 31 - 6x

Substitute y = 31 - 6x in the first equation

3x+2[31 - 6x] = 26

Expand

3x+ 62 - 12x = 26

Collect like terms

3x - 12x = 26 - 62

Evaluate

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Divide by - 9

x = 4

Substitute x = 4 in y = 31 - 6x

y = 31 - 6 * 4

y = 7

This means that the mean values are 4 and 7

To determine the correlation coefficient, we make y the subject in 3x+2y=26 and x the subject in 6x+y=31.

So, we have:

y = 13 - 3x/2 and x = 31/6 - 1/6y

The above means that:

Bxy = -1/6 and Byx = -3/2

The correlation coefficient is then calculated as:

r^2 = Bxy * Byx

r = -1/6 * -3/2

r = 0.25

Hence, the correlation coefficient between x and y is 0.25

The standard deviation of x

We have:

Var(y) = 4

In (a), we have:

y = 13 - 3x/2

To solve further, we make use of:

Var(y) = Var(ax + b) = a^2Var(x)

This gives

Var(y) = Var(13 - 3x/2) = 13^2 * Var(x)

So, we have:

Var(y) = 13^2 * Var(x)

Substitute 4 for Var(y)

4 = 13^2 * Var(x)

Divide both sides by 13^2

4/13^2 = Var(x)

Express 4 as 2^2

(2/13)^2 = Var(x)

So, we have:

Var(x) = (2/13)^2

Take the square root of both sides

SD(x) = 2/13

Hence, the standard deviation of x is 2/13

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