Question

find n if P (9,5) + 5P (9,4) =P (10,n)​

Answer 1

Answer:

1 answer

We have 9P5.9P4=10Pr. ⇒(9−5)!9!+5( 9−4)!9!=(10−r)!10! ⇒4!9!+55!9!=(10−r )!10! ⇒4!9!+4!9!=(10−r)!10! ⇒2×4!9!