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2 years ago

Solve the system of linear equations by substitution. 3x + y = -9 y=5x+7

Mathematics

1 answer:

11Alexandr11 [23.1K]2 years ago

8 0

Answer:

The solution is x = -2, y = -3

Step-by-step explanation:

Let's start with the equation 3x + y = -9

Substitute the y for 5x+7 seen in the second equation

Now you have 3x + (5x+7) = -9

Lets solve:

Let's add the x's

Now we have 8x + 7 = -9

Substracy seven from each side

Now we have 8x = -16

Now let's divide 8 on each side

Now we have x = -2

Now lets plug in -2 to the second equation

The second equation is y = 5x+7

When we plug in -2 we get y=5(-2)+7

We multiply

We now have y = -10+7

Add

y = -3

The solution is x = -2, y = -3

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3 years ago

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3 years ago

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Aleksandr [31]

Answer:

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So the answer for this case would be n=247 rounded up to the nearest integer

Step-by-step explanation:

We know that the standard deviation is :

$\sigma = 80$ represent the deviation

The margin of error is given by this formula:

$ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$ (a)

And on this case we have that ME =25 and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=(\frac{z_{\alpha/2} \sigma}{ME})^2$ (b)

The critical value for 95% of confidence interval now can be founded using the normal distribution and the critical value would be $z_{\alpha/2}=1.960$ , replacing into formula (b) we got:

$n=(\frac{1.960(80)}{25})^2 =246.73 \approx 247$

So the answer for this case would be n=247 rounded up to the nearest integer

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