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se considera E(x)=(2x+1)^2 -2(x-1)^2 +(1-x)(x+3) ;x=R. Aratati ca E(x) =(x+3)^2-7

Răspuns :

E(x)= (2x+1)²-2(x-1)²+(1-x)(x+3)= 4x²+4x+1-2x²+4x-2-x²-2x+3 ; grupam termenii asemenea si dupa efectuam calculele: 4x²-2x²-x²+4x+4x-2x+1-2+3= x²+6x+2
sau (x+3)²-7( daca desfiintam parantezele  obtinem x²+6x+2; ce am obtinut mai sus)
E(x) =(x+3)²-7