Permutation: In a race of 10 students, find the number of ways students can finish 1st, 2nd, and 3rd. In this case the order matters, so it is a permutation.
10 x 9 x 8 = 720 ways
Combination: In a class of 10 students, find the number of ways a group of 3 students can be selected to win a prize. In this case the order doesn't matter, so it's a combination.
10 x 9 x 8 / (3 x 2 x 1) = 120 ways
For this case we have, by definition:

So, we have:

On the other hand we have that by definition:

Thus, the expression can be written as:




So, we have:

Answer:

Answer:
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Step-by-step explanation: