Answer:
Option 4: (x+1)^2+(y-1)^2 = 16
Step-by-step explanation:
The radius of the given circle in attached picture is: 4 units
The center is denoted by (h,k) = (-1,1)
So,
The standard form of equation with center at (h,k) and radius r
(x-h)^2 + (y-k)^2 = r^2
Putting the values
(x-(-1))^2 + (y-1)^2 = 4^2
(x+1)^2+(y-1)^2 = 16
Hence option number 4 is correct ..
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Answer:
36.58% probability that one of the devices fail
Step-by-step explanation:
For each device, there are only two possible outcomes. Either it fails, or it does not fail. The probability of a device failling is independent of other devices. So 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.
A total of 15 devices will be used.
This means that 
Assume that each device has a probability of 0.05 of failure during the course of the monitoring period.
This means that 
What is the probability that one of the devices fail?
This is 


36.58% probability that one of the devices fail