[tex]E(x)=\frac{x^{2}-9}{x^{2}-3x} -\frac{3x+3}{x^{2}+x} ;\\=\frac{(x-3)(x+3)}{x(x-3)}-\frac{3(x+1)}{x(x+1)};\\=\frac{x+3}{x} -\frac{3}{x};\\=\frac{x+3-3}{x};\\=\frac{x}{x};\\ =1.[/tex]
x²-9=x²-3²=(x-3)(x+3)
A²-B²=(A+B)(A-B)
E(x)=(x-3)(x+3)/x(x-3)-3(x+1)/x(x+1)
E(x)=(x+3)/x-3/x
E(x)=(x+3-3)/x
E(x)=x/x
E(x)=1, (∀)x∈R-{-1, 0, 3}
