Tính

1) x+1/x-1 + x/x+1 - x/x^2 -1

2) 1/x+1+2x^2+1/2x^3+1+2x^3-2x^2/x^2-x+1

3) 2) x-2/x+2 + x/x-2 + 2x+4/4-x^2

4 ) x^2+1/x^2-9 - x/x+3 + 5/3-x