GIVEAWAY!!! <br> 50PTS + BRAINLIEST <br><br> 4(2x)−8x+4

Help...........................plz

Diano4ka-milaya [45]

Answer: (-1/4)

Step-by-step explanation:

This divides to -1/4

4 0

3 years ago

Read 2 more answers

There are 420 books on a bookcase with 7 shelves. Each shelf has the same number of books. How many books are on 4 shelves? 28 6

Ghella [55]

If we have 420 books for every 7 shelves and are looking for how many books are on 4 shelves, we need to set up fractional proportions.

We have 7 shelves for every 420 books, so we will have our first fraction like this:
7/420.
We also have 4 shelves for every x books, so our second fraction will be 4/x.

Set these fractions up as an equation.
7/420 = 4/x

To solve for x, we need to cross multiply the numerators of one fraction with the denominators of the other fraction.
In other words, multiply the top number of one fraction by the bottom number of the other question.

It should look like this:
7(x)
420(4)

7(x) = 7x
420(4) = 1680

Set your products up as an equation.
7x = 1680

Now to solve for x, we need to simplify.
Currently, x is being multiplied by 7.
To get x alone, divide 7x by 7.
Remember, what you do to one side of an equation, you must do to the other, so divide 1680 by 7.

7x / 7 = x
1680 / 7 = 240

You are left with:
x = 240.

For every 4 shelves you have 240 books.

I hope this helps!

3 0

3 years ago

Matt uses a compass and straightedge to construct parallel lines. Annie uses technology. In your own words describe how Matts co

ra1l [238]

Thank you for posting your question here at brainly. I hope the answer will help you. Feel free to ask more questions here.

Matt's steps will be more complicated since Annie is using a program to do the constructions hers would probably be precise and easy.

5 0

3 years ago

An experiment to investigate the survival time in hours of an electronic component consists of placing the parts in a test cell

mixer [17]

Answer:

a) The sample mean is of 49 and the sample standard deviation is of 11.7.

b) The range of the true mean at 90% confidence level is of 9.62 hours.

c) The prediction interval, at a 90% confidence level, of it's failure time is between 39.38 hours and 58.62 hours.

Step-by-step explanation:

Question a:

Sample mean:

$\overline{x} = \frac{34+40+46+49+61+64}{6} = 49$

Sample standard deviation:

$s = sqrt{\frac{(34-49)^2+(40-49)^2+(46-49)^2+(49-49)^2+(61-49)^2+(64-49)^2}{5}} = 11.7$

The sample mean is of 49 and the sample standard deviation is of 11.7.

b)Determine the range of the true mean at 90% confidence level.

We have to find the margin of error of the confidence interval. Since we have the standard deviation for the sample, the t-distribution is used.

The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So

df = 6 - 1 = 5

90% confidence interval

Now, we have to find a value of T, which is found looking at the t table, with 5 degrees of freedom(y-axis) and a confidence level of $1 - \frac{1 - 0.9}{2} = 0.95$ . So we have T = 2.0.150

The margin of error is:

$M = T\frac{s}{\sqrt{n}}$

In which s is the standard deviation of the sample and n is the size of the sample. So

$M = 2.0150\frac{11.7}{\sqrt{6}} = 9.62$

The range of the true mean at 90% confidence level is of 9.62 hours.

(c)If a seventh sample is tested, what is the prediction interval (90% confidence level) of its failure time.

This is the confidence interval, so:

The lower end of the interval is the sample mean subtracted by M. So it is 49 - 9.62 = 39.38 hours.

The upper end of the interval is the sample mean added to M. So it is 49 + 9.62 = 58.62 hours.

The prediction interval, at a 90% confidence level, of it's failure time is between 39.38 hours and 58.62 hours.

4 0

3 years ago

Jenna and Mike are given two points of a triangle, A(-2,-4) and B(8,6).

Taya2010 [7]

Answer: B) neither Jenna and Mike are correct.

Step-by-step explanation: If you calculate the distance between points B and A, then the points that Mike and Jenna gave, all of the sides would be different.

4 0

2 years ago

GIVEAWAY!!! 50PTS + BRAINLIEST 4(2x)−8x+4