Question

Fie numerele : n –3 ; 2n+1 ; 2n –1 , unde n Z ∈ .
a) AflaŃi suma numerelor ştiind căprodusul lor este 0
 b) Aflati produsul numerelor ştiind că suma lor este ( +2 ).

Answer 1

(n-3)(2n-1)(2n+1)= 0
n= 0 +3 = 3
n= 0 + 1 : 2= 1 : 2= 0,5
n= 0 -1 : 2= -1 : 2= -0,5.

b)n-3 +2n+1+2n-1= 2
5n-3=2
5n= 3+2
n= 5: 5
n= 1
(n-3)(2n+1)(2n-1)= (1-3) (2+1)(2-1)= -2 x 3 x 1= -6.

Answer 2

a) (n-3)(2n-1)(2n+1)=0
n-3=0⇒n=3
2n-1=0⇒n=1/2
2n+1=0⇒n=-1/2

n-3+2n-1+2n+1=5n-3
daca n=3⇒5n-3=12
daca n=1/2⇒5n-3=-1/2
daca n=-1/2⇒5n-3=-11/2

b)n-3+2n-1+2n+1=5n-3=2⇒n=1
(n-3)(2n-1)(2n+1)=-2*1*2=4