SOLUTION: I know I already asked for help on similar problems, but this one is sorta really confusing me; (I should subtract it) 2x^2y-5xy^2+2 - -x^2y+2xy^2+2 ----------- ----- (

To subtract, rewrite the problem as an addition
by changing all the signs on the second row.  
Then add.


  2x^2y - 5xy^2 + 2
- -x^2y + 2xy^2 + 2
-------------------

Since it's SUBTRACT, you rewrite the problem
as an addition by changing all the signs on the 
second row, and put a 1 in front of the x^2y:

  2x^2y - 5xy^2 + 2
+ 1x^2y - 2xy^2 - 2
-------------------

Now add the 2x^2y and the 1x^2y and get 3x^2y:

  2x^2y - 5xy^2 + 2
+ 1x^2y - 2xy^2 - 2
-------------------
  3x^2y

Now add the second column -5xy^2 and -2xy^2 and get
-7xy^2

  2x^2y - 5xy^2 + 2
+ 1x^2y - 2xy^2 - 2
-------------------
  3x^2y - 7xy^2

Now add the third column +2 and -2 and get 0. So

  2x^2y - 5xy^2 + 2
+ 1x^2y - 2xy^2 - 2
-------------------
  3x^2y - 7xy^2 + 0

You really don't have to write the + 0. The 
answer is 3x^2y - 7xy^2 

-----------------

  6x + 9
- 2x + 4
---------
 
Since it is subtract, you change all the signs on
the second row:

  6x + 9
+-2x - 4
--------- 

Now add the 6x and the -2x and get 4x:

  6x + 9
+-2x - 4
--------- 
  4x

Now add the +9 and the -4 and get +5:

  6x + 9
+-2x - 4
--------- 
  4x + 5

Edwin