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5. Se considera expresia E(x)= (1+x)(1-x)+(x+2)²-2(x+2) , unde x este un numar real.
Determinati numarul real a pentu care E(a)=-1


Răspuns :

E(x)= (1+x)(1-x)+(x+2)²-2(x+2); x∈R

E(x)= 1-x²+(x+2)(x+2-2)

E(x)= 1-x²+(x+2)•x

E(x)= 1-x²+x²+2x

E(x)=1+2x

E(a)=1+2a

1+2a=-1

2a= -2 => a= -1