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A system consisting of one original unit plus a spare can function for a random amount of time X. If the probability density of X is given (ini units of months) by

f(x)={kxe⁻ˣ/³, x>0
{0, elsewhere,
what is the probability that the system functions for at least five months?

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Final answer:

The probability that the system functions for at least five months is found by integrating the given probability density function from 5 to infinity, which requires determining the constant k to ensure that the probability density function is properly normalized.

Step-by-step explanation:

The student is asking about the probability that a system functions for at least five months, where the system's operational time X follows a certain probability density function. To find this probability, we'll integrate the given function for all values that are greater than or equal to 5. Since the area under the probability density function represents the probability, we need to find the area from 5 to infinity under the function f(x) = kxe-(x/3) for x > 0.

To start, we need to determine the constant k. Since the total area under the probability density function must equal 1 (as probability is always between 0 and 1), we can find k by setting up the integral of f(x) from 0 to infinity equal to 1 and solving for k.

Once k is known, we can calculate the desired probability. The probability that the system functions for at least five months is:

P(X ≥ 5) = ∫5∞ kxe-(x/3) dx

This integral can be solved using integration by parts or substituting and applying improper integral techniques. If the decay parameter m from this distribution equated to the one from an exponential distribution with mean μ, it would be m = 1/μ. However, the given density function does not appear to match the standard exponential distribution form, so an exact comparison or direct calculation using the decay parameter cannot be made without knowing the value of k.

Once integrated, the result will give the probability that the system will continue to operate for at least 5 months. To solve this problem, intermediate calculus and knowledge on probability distributions are required.

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