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2 years ago

14

1. (x + 2) (x +5)

1 answer:

madam [21]2 years ago

3 0

Step-by-step explanation:

el trabajo que pusiste es muy falso

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2 years ago

The amount of time required for an oil and filter change on an automobile is normally distributed with a mean of 45 minutes and

Firdavs [7]

Answer:

1a

$P(39 < X < 48 ) = 0.8767$

1b

95% of all sample means will fall between $40.1 < \mu < 49.9$

1c

$\= x = 41. 795$

2

$n = 25$

Step-by-step explanation:

From the question we are told that

The mean is $n = 45$

The population standard deviation is $\sigma = 10$

The sample size is n = 16

Generally the standard error of the mean is mathematically represented as

$\sigma_{x} = \frac{ \sigma}{\sqrt{n} }$

=> $\sigma_{x} = \frac{ 10 }{\sqrt{16 } }$

=> $\sigma_{x} = 2.5$

Generally the probability that the sample mean will be between 39 and 48 minutes is

$P(39 < X < 48 ) = P( \frac{ 39 - 45}{ 2.5} < \frac{X - \mu }{\sigma } < \frac{ 48 - 45}{ 2.5} )$

=> $P(39 < X < 48 ) = P(-2.4 < Z< 1.2 )$

=> $P(39 < X < 48 ) = P( Z< 1.2 ) - P(Z < -2.4)$

From the z table the area under the normal curve to the left corresponding to 1.2 and -2.4 is

=> $P( Z< 1.2 ) = 0.88493$

and

$P( Z< - 2.4 ) = 0.0081975$

So

$P(39 < X < 48 ) = 0.88493 -0.0081975$

=> $P(39 < X < 48 ) = 0.8767$

From the question we are told the confidence level is 95% , hence the level of significance is

$\alpha = (100 - 95 ) \%$

=> $\alpha = 0.05$

Generally from the normal distribution table the critical value of is

$Z_{\frac{\alpha }{2} } = 1.96$

Generally the margin of error is mathematically represented as

$E = Z_{\frac{\alpha }{2} } * \frac{\sigma }{\sqrt{n} }$

=> $E = 1.96 * 2.5$

=> $E =4.9$

Generally the 95% of all sample means will fall between

$\mu -E < and \mu +E$

=> $45 -4.9\ and \ 45 + 4.9$

Generally the value which 90% of sample means is greater than is mathematically represented

$P( \= X > \= x ) = 0.90$

=> $P( \= X > \= x ) = P( \frac{\= X - \mu }{ \sigma_x} > \frac{\= x -45 }{ 2.5} ) = 0.90$

=> $P( \= X > \= x ) = P( Z > z ) = 0.90$

Generally from the z-table the critical value of 0.90 is

$z = -1.282$

$\frac{\= x -45 }{ 2.5} = -1.282$

=> $\= x = 41. 795$

Considering question 2

Generally we are told that the standard deviation of the mean to be one fifth of the population standard deviation, this is mathematically represented as

$s = \frac{1}{5} \sigma$

Generally the standard deviation of the sample mean is mathematically represented as

$s = \frac{\sigma }{ \sqrt{n} }$

=> $\frac{1}{5} \sigma = \frac{\sigma }{ \sqrt{n} }$

=> $n = 5^2$

=> $n = 25$

5 0

2 years ago

Sviatoslav solved the quadratic equation x^2-x-1=0 by completing the square. In the process, he came up with the equivalent equa

zimovet [89]

Answer:

$x=\frac{1+\sqrt5}{2}$ and $x=\frac{1-\sqrt5}{2}$

and b= $\frac{5}{4}$

Step-by-step explanation:

We are given that a quadratic equation

$x^2-x-1=0$

We have to solve the equation by completing square and find the value of b.

$(x)^2-2\times x\times \frac{1}{2}+(\frac{1}{2})^2-(\frac{1}{2})^2-1=0$

$(x-\frac{1}{2})^2-\frac{1}{4}-1=0$

$(x-\frac{1}{2})^2-\frac{1-4}{4}=0$

$(x-\frac{1}{2})-\frac{5}{4}=0$

$(x-\frac{1}{2})^2-(\frac{\sqrt5}{2})^2=0$

$(x-\frac{1}{2})^2=(\frac{\sqrt5}{2})^2$

$x-\frac{1}{2}=\frac{\sqrt5}{2}$ and $x-\frac{1}{2}=-\frac{\sqrt5}{2}$

$x=\frac{\sqrt5}{2}+\frac{1}{2}=\frac{1+\sqrt5}{2}$

And $x=\frac{1}{2}-\frac{\sqrt5}{2}=\frac{1-\sqrt5}{2}$

Therefore, $x=\frac{1+\sqrt5}{2}$ and $x=\frac{1-\sqrt5}{2}$

and b= $\frac{5}{4}$

6 0

2 years ago