Permutation

Question

Evaluate the expression
19 P 2

4 P r if there is no r would the answer be
just 4 or 0

Answer 1

19 P 2
= 19!/(19-2)!
= 19(18)(17!)/(17!
= 19(18)
= 342

If by "if there is no r" you mean "if the value of r = 0"

then
4P0
= 4!/(4-0)!
= 1

Answer 2

thank you