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yKpoI14uk [10]
2 years ago
7

According to a study, 91% of all adults have a cell phone. An employee of a cell phone company attends a community event and has

a special offer to give to first time cell phone owners. If she randomly selects adults in attendance at the event and cell phone ownership is independent from adult to adult, what is the probability that she asks 21 adults total to find the first one that does not own a cell phone?
Mathematics
1 answer:
umka2103 [35]2 years ago
6 0

Answer:

(0.91)^{20}(0.09)

Step-by-step explanation:

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If a(x) = 3x + 1 and b (x) = StartRoot x minus 4 EndRoot, what is the domain of (b circle a) (x)?
kiruha [24]

Answer:

[1,\infty)

Step-by-step explanation:

b(x)=\sqrt{x-4}

a(x)=3x+1

Since we want to know the domain of (b \circ a)(x), let's first consider the domain of the inside function, that is, that of a(x)=3x+1. Every polynomial function has domain all real numbers.

So we can plug anything for function a and get a number back.

Now the other function is going to be worrisome because it has a square root. You cannot take square root of negative numbers if you are only considering real numbers which that is the case with most texts.

Let's find (b \circ a)(x) and simplify now.

(b \circ a)(x)

b(a(x))

b(3x+1)

\sqrt{(3x+1)-4}

\sqrt{3x+1-4}

\sqrt{3x-3}

Now again we can only square root positive or zero numbers so we want 3x-3 \ge 0.

Let's solve this to find the domain of (b \circ a)(x).

3x-3 \ge 0

Add 3 on both sides:

3x \ge 3

Divide both sides by 3:

x \ge 1

So we want x to be a number greater than or equal to 1.

The option that says this is [1,\infty)

-------------------------------

Give an example why option A fails:

A number in the given set is -2.

a(x)=3x+1

b(x)=\sqrt{x-4}

So a(-2)=3(-2)+1=-6+1=-5 and b(-5)=\sqrt{-5-4}=\sqrt{-9} \text{ which is not real}.

Give an example why option B fails:

A number in the given set is 0.

a(x)=3x+1

b(x)=\sqrt{x-4}

So a(0)=3(0)+1=0+1=1 and b(1)=\sqrt{1-4}=\sqrt{-3} \text{ which is not real}.

Give an example why option D fails:

While all the numbers in set D work, there are more numbers outside that range of numbers that also work.

A number not in the given set that works is 3.

a(x)=3x+1

b(x)=\sqrt{x-4}

So a(3)=3(3)+1=9+1=10 and b(1)=\sqrt{10-4}=\sqrt{6} \text{ which is real}.

4 0
2 years ago
Read 2 more answers
The double number line shows that 3 back-to-school packages contain 36 pencils.
lord [1]

Answer:

The answer is A

Step-by-step explanation:

i just got it right

7 0
2 years ago
Part B: Find an irrational number that is between 9.5 and 9.7. Explain why it is irrational. Include the decimal approximation o
fgiga [73]
Irrational number between 9.5 and 9.7...

9.678937... (never ending)...it is irrational because it cannot be made into a fraction because it is infinite.

the decimal approximation to the nearest hundredth is : 9.68

4 0
2 years ago
Assume the returns from an asset are normally distributed. The average annual return for the asset is 17.4 percent and the stand
Jlenok [28]

Answer:

0.13%

Step-by-step explanation:

Mean, u = 17.4%

standard deviation, sd = 27.5%

We are looking for the probability that the money will double in value. Therefore we are looking for the value of x = 100% (meaning the value is 100% more that the previous year)

Find the value of z-score

z = (x-u)/sd

  = (100 - 17.4) / 27.5 = 3.003

Find the z score using the z-table

From z-table at P(z<3.003) = 0.9987

So, for the probability that it the money will be double is

P (Z>2.8982) = 1 - P(z<2.8982)

                      = 1- 0.9987

                      = 0.0013  = 0.13%

6 0
2 years ago
While exercising Julie found that her. Heart was beating 12times every 5 seconds how many times was it beating per min
Vika [28.1K]
12 times / 5 seconds * (60 seconds / 1 min) = 144 times / min
7 0
2 years ago
Read 2 more answers
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