SOLUTION: The problem is P(n,2)=42, find n. The instructor gave the answer for n, which is 7. I figured out the formula knowing the answer is 7, which is n!/(n-k)! I need to know the formul

Algebra ->  Permutations -> SOLUTION: The problem is P(n,2)=42, find n. The instructor gave the answer for n, which is 7. I figured out the formula knowing the answer is 7, which is n!/(n-k)! I need to know the formul      Log On


   



Question 147870This question is from textbook Mathematical Excursions
: The problem is P(n,2)=42, find n. The instructor gave the answer for n, which is 7. I figured out the formula knowing the answer is 7, which is n!/(n-k)!
I need to know the formula to figure out how to get the value of n. Thank you.
This question is from textbook Mathematical Excursions

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
P(n,2)=42, find n.
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n!/(n-2)! = 42
n(n-1) = 42
n^2 -n - 42 = 0
(n-7)(n+6) = 0
Positive answer:
n = 7
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Cheers,
Stan H.