Explicație pas cu pas:
1/(x-1) - 1/(x+1) +1/(x²-1)=
1/(x-1)-1/(x+1)+1/(x-1)(x+1)=
(x+1)/(x+1)(x-1)-(x-1)/(x+1)(x-1)+1/(x-1)(x+1)=
(x+1-x+1+1)/(x+1)(x-1)=
3/(x+1)(x-1)
E(x)=3/(x+1)(x-1) * (1-x²)/3=>
E(x)=(1-x²)/(x+1)(x-1)=>
E(x)=(1+x)(1-x)/(x+1)(x-1)=>
E(x)=(1-x)/(x-1)=>E(x)= -(x-1)/(x-1)=>E(x)=-1