You are a landscaper and need to mulch 15 yards of plant beds. You have 20 bags of mulch and each bag covers 3 feet.
2 answers:
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Answer:
The probability that the student answers at least seventeen questions correctly is .
Step-by-step explanation:
Let the random variable <em>X</em> represent the number of correctly answered questions.
It is provided all the questions have five options with only one correct option.
Then the probability of selecting the correct option is,
There are <em>n</em> = 20 question in the exam.
It is also provided that a student taking the examination answers each of the questions with an independent random guess.
Then the random variable can be modeled by the Binomial distribution with parameters <em>n</em> = 20 and <em>p</em> = 0.20.
The probability mass function of <em>X</em> is:
Compute the probability that the student answers at least seventeen questions correctly as follows:
Thus, the probability that the student answers at least seventeen questions correctly is .
Answer:
A
Step-by-step explanation:
We are given the function f and its derivative, given by:
Remember that f(x) is decreasing when f'(x) < 0.
And f(x) is increasing when f'(x) > 0.
Firstly, determining our zeros for f'(x), we see that:
Since a is a (non-zero) positive constant, -a is negative.
We can create the following number line:
<-----(-a)-----0-----(a)----->
Next, we will test values to the left of -a by using (-a - 1). So:
Since a is a positive constant, (2a + 1) will be positive as well.
So, since f'(x) > 0 for x < -a, f(x) increases for all x < -a.
To test values between -a and a, we can use 0. Hence:
This will always be negative.
So, since f'(x) < 0 for -a < x < a, f(x) decreases for all -a < x < a.
Lasting, we can test all values greater than a by using (a + 1). So:
Again, since a > 0, (2a + 1) will always be positive.
So, since f'(x) > 0 for x > a, f(x) increases for all x > a.
The answer choices ask for the domain for which f(x) is decreasing.
f(x) is decreasing for -a < x < a since f'(x) < 0 for -a < x < a.
So, the correct answer is A.