Question

Cine ma poate ajuta la acest exercitiu?????
a) 6!*13-5!*12; b) 5!-1!-2!-3!-4!; c) 7!-6!+5!-4!;

Answer 1

Obs. 1*2*3*...*n = n!   .

a).  6!*13-5!*12= \

     = (1*2*3*4*5*6)*13 - (1*2*3*4*5)*12=5!*(6*13-12)=

     = 5!*66 = 7920 ;

b).  5! - 1! - 2! - 3! - 4! =

     =(1*2*3*4*5)-(1)-(1*2)-(1*2*3)-(1*2*3*4)=120-1-2-6-24=

     = 120 - 33 = 87 ;

c).  7!-6!+5!-4! =

     = (1*2*3*4*5*6*7)-(1*2*3*4*5*6)+(1*2*3*4*5)-(1*2*3*4) =

     = 5040 - 720 + 120 - 24 = 4416 ;