Thực hiện phép tính: (1/x^2 - 2x + 1) + (2/x^2 + 2x)

1. thuc hien phep tinh :
a, ( 1 / x^2 - 2x +1 ) + ( 2 / x^2 + 2x )
b, ( -3 / 2x + 6 ) + ( -2 / x^2 + 6x + 9 )
c, ( 2x / x^2 + 2xy ) + ( y / xy - 2y^2 ) + ( 4 / x^2 - 4y^2 )