Question 70713
{{{((7x^2y-4xy+9xy^2)-(8x^2y+8xy+8xy^2))}}}
[Start by trying to combine like-terms within the parenthesis)
.
{{{(7x^2y-4xy+9xy^2-8x^2y-8xy-8xy^2)}}}
[There are not any like-terms so eliminate the parenthesis.  Multiply-through by the negative sign]
.
{{{(7x^2y-8x^2y-4xy-8xy+9xy^2-8xy^2)}}}
[Again, try to combine like-terms]
.

{{{(-1x^2y-12xy+1xy^2)}}}
{{{(-x^2y-12xy+xy^2)}}} [All like-terms have been combined]