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Mathematics 9 Online
OpenStudy (anonymous):

nP5 =42(nP3)

OpenStudy (abb0t):

56

OpenStudy (anonymous):

can u clarify? and tell me the steps?

jimthompson5910 (jim_thompson5910):

n P 5 = 42( n P 3 ) n*(n-1)*(n-2)*(n-3)*(n-4) = 42( n*(n-1)*(n-2) ) Let z = n*(n-1)*(n-2) which would give us z(n-3)*(n-4) = 42z (n-3)(n-4) = 42 n^2 - 7n + 12 = 42 n^2 - 7n + 12 - 42 = 0 n^2 - 7n - 30 = 0 (n - 10)(n + 3) = 0 n - 10 = 0 or n+3 = 0 n = 10 or n = -3 Since n > 0, this means that the only solution is n = 10

OpenStudy (abb0t):

oh, this was a real question? lol i thought it look'd like something familiar. Lol

OpenStudy (anonymous):

i saw this on the internet is this right? n!/(n - 5)! = 42 * n! / (n - 3)! (n - 3)(n - 4) = 42 n = 10

jimthompson5910 (jim_thompson5910):

yes that's correct (missing a few steps, but has the right idea and answer)

OpenStudy (anonymous):

oh ok well thanks

jimthompson5910 (jim_thompson5910):

np

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