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Se considera expresia. E(x)=(x+3)la puterea 2 +2(x-4)(x+3)+(x-4)la puterea 2 ,dunde x apratine lui R.
Aratati ca E(x) =(2x-1)la puterea 2


Răspuns :

formula de calcul prescurtat (a+b)^2=a^2+2ab+b^2
(x+3)^2=a^2
2(x-4)(x+3)=2ab
(x-4)^2=b^2 

⇒(x+3)^2+2(x-4)(x+3)+(x-4)^2=(x+3+x-4)^2=(2x-1)^2.
Asa cred ca vine. :).