Tính rút gọn biểu thức

1/ x^2/3x+6  + 4x+4/3x+6 
2/ 9x=3/4x-1 -  3x/1-4x
3/ 2x/x-2      +   3x/x+2   - x(x+6)/x^2-4
4/ x^2-2/3x+6  + 4x+6/3x+6  
5/ x-3/x+3  - 3/x-3  +  6x/x^2-9
6/ x-14/x^2-4x     -   3/2x  +  x+1/2x-8
7/ x+2y/x+y -  y/x+y
8/ x^2/x+2y  +  4xy+4y^2/x+2y
9/ x+1/x-2  + 4x+2  + 7x-2/x^2 -4
10/ 1-x/x+3  + x/x-3  + 6x/9-x^2
11/ 3x+2/2x-1  + 6x+9/2x-1
12/ x-3/x+1 - x+2/x-1 + 8x/x^2-1 
13/2x/x+2 + 4/x+2
14/ 4x+1/7x^2 - 1-2x/7x^2
15/ x^2/x^2+2x - 2/x  + 2/x+2
16/ x/x+1  + 1/x+1