Question

primele 2 exerciții plsssss

Answer 1

Verificam P(1) :

1=(1x(1+1))/2

1=2/2

1=1

Presupunem adevarat P(k):

1+2+...+k=(k(k+1))/2

Demonstram P(k+1)

1+2+3+....+k+(k+1)=((k+1)(k+2))/2

(k(k+1))/2+(k+1)=(k(k+1)+2(k+1))/2=((k+1)(k+2))/2

Rezulta P(n) adevarat