Come valuti # 9P4 #?
Risposta:
# " "^9P_4" "=3024#
Spiegazione:
# " "^nP_r" "#ha la formula
# " "^nP_r" "=(n!)/((n-r)!)#
so# " "^9P_4" "=(9!)/((9-4)!)#
so# " "^9P_4" "=(9!)/(5!)=(9xx8xx7xx6xxcancel(5!))/cancel((5!)#
# " "^9P_4" "=(9!)/(5!)=9xx8xx7xx6=3024#