Thực hiện phép tính: (5 / 2x^2y) + (3 / 5xy^2) + (x / y^3)

1. thuc hien phep tinh ;
a, ( 5 / 2x^2y ) + ( 3 / 5xy^2 ) + ( x / y^3 )
b, ( 3x + 5 / x^2 - 5x ) + ( 25x- x / 25 - 5x )
c, ( 1 /x - 5x^2 ) - ( 25x - 15 / 25x^2 - 1 )
d, ( 1 / x^3 - 1 ) + ( 1 / 1 - x ) + ( 1 / x^2 + x + 1 )