Question

A) If "P2= 20 then the value of n is .......​

Answer 1

Answer:

nP2=20

n!/(n-2)!=20

n(n-1)(n-2)!/(n-2)!=20

n(n-1)=20

n²-n-20=0

n²-5n+4n-20=0

n(n-5)+4(n-5)=0

n+4=0 or n-5=0

n=-4 or n=5

Since n is positive, n=5