[tex]\it a)\ \ Vom\ \ nota\ \ x+5=a,\ \ x-4=b\\ \\ E=a^2+2ab+b^2=(a+b)^2 \Rightarrow E(x)=(x+5+x-4)^2=(2x+1)^2[/tex]
[tex]\it b)\ E(x)=(2x+1)^2=(1+2x)^2 \\ \\ E(n)\cdot E(-n)=(1+2n)^2\cdot(1-2n)^2=[(1+2n)(1-2n)]^2=(1-4n^2)^2\\ \\ Pentru\ \ n=\sqrt2, vom\ avea :\\ \\ E(\sqrt2)\cdot E(-\sqrt2)=(1-4\cdot2)^2=(1-8)^2=(-7)^2=(-7)\cdot(-7)=49[/tex]
