Answer:
0.1502 = 15.02% probability that exactly 13 of them use their smartphones in meetings or classes
Step-by-step explanation:
For each adult smartphone users, there are only two possible outcomes. Either they use the phone in meetings or classes, or they do not. The probability of an adult using the phone in these settings is independent of any other adult. This means that we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which 
is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
58% use them in meetings or classes
This means that 
20 adult smartphone users are randomly selected
This means that 
Find the probability that exactly 13 of them use their smartphones in meetings or classes.
This is 
. So
0.1502 = 15.02% probability that exactly 13 of them use their smartphones in meetings or classes
4/5 P + 6 is the answer. just put it in whatever order youd like
The gradient/slopes of perpendicular lines are NEGATIVE reciprocal. This means that their product is -1.
The question regards composite functions. A composite function is a function composed of more than one function. Sorry for saying the word function so many times there, it's just what it is...
The phrase f(g(x)) means 'perform g on an input x, then perform f on the result'. You can then see that there are many options for f(x) and g(x) here, in fact an infinite number of one were to be ridiculous about it.
However a sensible choice might be g(x) = x^2, and f(x) = 2/x + 9. Checking:
g(x) = x^2
f(g(x)) = 2/(x^2) + 9
That is the first question dealt with. Next up is Q2. It is relatively simple to show that these functions are inverses. If you start with a value x, apply a function and then apply the function's inverse, you should return to the same starting value x. To take a common example, within a certain domain, sin^-1(sin(x)) = x.
f(g(x)) = (sqrt(3+x))^2 - 3 = 3 + x - 3 = x
g(f(x)) = sqrt(x^2 - 3 + 3) = sqrt(x^2) = x
A final note is that this is only true for a certain domain, that is x <= 0. This is because y = x^2 is a many-to-one function, so unrestricted it does not have an inverse. Take the example to illustrate this:
If x = -2, f(x) = (-2)^2 - 3 = 4 - 3 = 1
Then g(f(x)) =sqrt(1 + 3) = sqrt(4) = 2 (principal value).
However the question isn't testing knowledge of that.
I hope this helps you :)
