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3 years ago

Can someone help me with this

Mathematics

2 answers:

Leviafan [203]3 years ago

6 0

By illegal I'm guessing it means undefined, so when the denominator is equal to 0 because you can't divide by 0
you can either use the quadratic equation or sub the values from the multiple choice to find it. in this case it's easier to use the values given in the multiple choice
b^2-2b-8=0
b^2-2b=8
(-2)^2-2 (-2)=8
4--4=8
4+4=8
so -2 is one of the values
(-4)^2-2 (-4)=8
16+8=8
16+8=24
so -4 isnt one of the values
(4)^2-2 (4)=8
16-8=8
so 4 is one of the values
(-5)^2-2 (-5)=8
25+10=8
25+10=35
so -5 isn't one of the values
So because we know that the values are -2 and 4, and -5 and -4 aren't values, we can conclude the answer is B

sweet-ann [11.9K]3 years ago

4 0

As this is a fraction, we need to find values where the denominator is equal to 0.

$b^2-2b-8=0$
$(b-4)(b+2)$
$b=4 \vee b=-2$

So the answer is B.

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All four angles of a rectangle are 90° each.
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2 years ago

Mrs. Smith left a 15% tip for a dinner that cost $62.40. About how much tip did Mrs. Smith leave?

Veronika [31]

Given :- 

Mrs. Smith left a 15% tip for a dinner that cost $62.40.

To find :- 

About how much tip did Mrs. Smith leave?

Solution :- 

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$ 62.40 * 15%
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2 years ago

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What is 2/5 plus 1/3

leva [86]

First, you need to get the denominators (the bottom number) the same. The smallest number to get them to is 15.

So, what you need to do is take 2/5 and multiply the bottom by 3 to get 15, and since you did it to the bottom, you need to do it to the top too. So you would get, 6/15.

Then, for 1/3, take the bottom number and multiply it by 5. Then, since you did it to the bottom, do it to the top as well. You would get 5/15.

Then, you need to put them side by side. You don't add the bottom, so your denominator would remain 15, but your numerator (top) would get added.

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3 years ago

Solve this equation. 2/3x−1/5x=x−1

KonstantinChe [14]

Answer:

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Step-by-step explanation:

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3 years ago

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A physical fitness association is including the mile run in its secondary-school fitness test. The time for this event for boys

Luba_88 [7]

Answer:

$z=-1.28$

And if we solve for a we got

$a=470 -1.28*60=393.2$

So the value of height that separates the bottom 10% (Fastest 10%) of data from the top 90% is 393.2.

so if the time is 393.2 or lower a boy would earn a certificate of recognition from the fitness association

Step-by-step explanation:

Previous concepts

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".

Solution to the problem

Let X the random variable that represent the time for this event of a population, and for this case we know the distribution for X is given by:

$X \sim N(470,60)$

Where $\mu=470$ and $\sigma=60$

NOTE: For this case the fastest 10% is on the lower tail of the distribution

For this part we want to find a value a, such that we satisfy this condition:

$P(X>a)=0.9$ (a)

$P(X$ (b)

Both conditions are equivalent on this case. We can use the z score again in order to find the value a.

As we can see on the figure attached the z value that satisfy the condition with 0.1 of the area on the left and 0.9 of the area on the right it's z=-1.28. On this case P(Z<-1.28)=0.1 and P(z>-1.28)=0.9

If we use condition (b) from previous we have this:

$P(X$

$P(z$

But we know which value of z satisfy the previous equation so then we can do this:

$z=-1.28$

And if we solve for a we got

$a=470 -1.28*60=393.2$

So the value of height that separates the bottom 10% (Fastest 10%) of data from the top 90% is 393.2.

so if the time is 393.2 or lower a boy would earn a certificate of recognition from the fitness association

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3 years ago