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3 years ago

What are the solutions of 12 – x2 = 0?

2 answers:

4 0

$- {x}^{2} + 12 = 0 \\ - x {}^{2} + 12 - 12 = 0 - 12 \\ - {x}^{2} = - 12 \\ {x}^{2} = 12 \\ x = + \sqrt{12 \:} and - \sqrt{12}$

Kazeer [188]3 years ago

4 0

Answer:

x = 2√3 and -2√3

Step-by-step explanation:

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3/4x4/7 will be A less than B equal to C greater than 3/4

Troyanec [42]

Answer:

less than, this is scaling dude

Step-by-step explanation:

7 0

2 years ago

Plot the vertex of f(x) = (x − 2)2 + 2.<br> PLEASE HELP ME IM UPSET

8090 [49]

<h3>Answer: The vertex is located at (2, 2)</h3>

====================================================

Explanation:

The general vertex form is

y = a(x-h)^2 + k

When we compare the function your teacher gave you to this template, then we see that

a = 1
h = 2
k = 2

The vertex is therefore (h,k) = (2,2)

The value of 'a' has no role in the vertex's location. This value determines how vertically stretched or compressed the parabola will be. Also, it determines if the parabola opens upward or downward (a > 0 for upward; a < 0 for downward).

3 0

3 years ago

Let X1 and X2 be independent random variables with mean μand variance σ².

My name is Ann [436]

Answer:

a) $E(\hat \theta_1) =\frac{1}{2} [E(X_1) +E(X_2)]= \frac{1}{2} [\mu + \mu] = \mu$

So then we conclude that $\hat \theta_1$ is an unbiased estimator of $\mu$

$E(\hat \theta_2) =\frac{1}{4} [E(X_1) +3E(X_2)]= \frac{1}{4} [\mu + 3\mu] = \mu$

So then we conclude that $\hat \theta_2$ is an unbiased estimator of $\mu$

b) $Var(\hat \theta_1) =\frac{1}{4} [\sigma^2 + \sigma^2 ] =\frac{\sigma^2}{2}$

$Var(\hat \theta_2) =\frac{1}{16} [\sigma^2 + 9\sigma^2 ] =\frac{5\sigma^2}{8}$

Step-by-step explanation:

For this case we know that we have two random variables:

$X_1 , X_2$ both with mean $\mu = \mu$ and variance $\sigma^2$

And we define the following estimators:

$\hat \theta_1 = \frac{X_1 + X_2}{2}$

$\hat \theta_2 = \frac{X_1 + 3X_2}{4}$

Part a

In order to see if both estimators are unbiased we need to proof if the expected value of the estimators are equal to the real value of the parameter:

$E(\hat \theta_i) = \mu , i = 1,2$

So let's find the expected values for each estimator:

$E(\hat \theta_1) = E(\frac{X_1 +X_2}{2})$

Using properties of expected value we have this:

$E(\hat \theta_1) =\frac{1}{2} [E(X_1) +E(X_2)]= \frac{1}{2} [\mu + \mu] = \mu$

So then we conclude that $\hat \theta_1$ is an unbiased estimator of $\mu$

For the second estimator we have:

$E(\hat \theta_2) = E(\frac{X_1 + 3X_2}{4})$

Using properties of expected value we have this:

$E(\hat \theta_2) =\frac{1}{4} [E(X_1) +3E(X_2)]= \frac{1}{4} [\mu + 3\mu] = \mu$

So then we conclude that $\hat \theta_2$ is an unbiased estimator of $\mu$

Part b

For the variance we need to remember this property: If a is a constant and X a random variable then:

$Var(aX) = a^2 Var(X)$

For the first estimator we have:

$Var(\hat \theta_1) = Var(\frac{X_1 +X_2}{2})$

$Var(\hat \theta_1) =\frac{1}{4} Var(X_1 +X_2)=\frac{1}{4} [Var(X_1) + Var(X_2) + 2 Cov (X_1 , X_2)]$

Since both random variables are independent we know that $Cov(X_1, X_2 ) = 0$ so then we have:

$Var(\hat \theta_1) =\frac{1}{4} [\sigma^2 + \sigma^2 ] =\frac{\sigma^2}{2}$

For the second estimator we have:

$Var(\hat \theta_2) = Var(\frac{X_1 +3X_2}{4})$

$Var(\hat \theta_2) =\frac{1}{16} Var(X_1 +3X_2)=\frac{1}{4} [Var(X_1) + Var(3X_2) + 2 Cov (X_1 , 3X_2)]$

Since both random variables are independent we know that $Cov(X_1, X_2 ) = 0$ so then we have:

$Var(\hat \theta_2) =\frac{1}{16} [\sigma^2 + 9\sigma^2 ] =\frac{5\sigma^2}{8}$

7 0

3 years ago

Dan bought a truck for $29,800. The value of the truck depreciated at a constant rate per year. The table shows the value of the

leonid [27]

Answer:

A) f(t) = 29,800(0.89)^t

Step-by-step explanation:The truck value decreases by 11% each year.

The present value of the truck was $29,800.

29,800 x 0.11 = 3,728 dollars lost from value.

29,800 - 3,728 = 26,522, the value of the truck after one year.

26,522 x 0.11 = 2,917.42 cash lost from value.

26,522 - 3,728 = 23,604.58, the value of the truck after two years.

Therefore, the answer is A) f(t) = 29,800(0.89)^t.

7 0

2 years ago

A tortoise is walking in the desert. It walks at a speed of 7 meters per minute for 8.96 meters. For how many minutes does it wa

Licemer1 [7]

Answer:

1.28 minutes

Step-by-step explanation:

Given data

Speed= 7 meters per minute

Distance= 8.96 meters

We know that the expression for the Speed, Distance, and time is given as

Speed= Distance/Time

TIme= Distance/Speed

Substitute

Time= 8.96/7

Time= 1.28 minutes

7 0

3 years ago