## Algebra: A Combined Approach (4th Edition)

$6x^{2}y^{2}-9x^{2}y+8xy^{2}-y^{2}-4$
$(5x^{2}y^{2}+3-9x^{2}y+y^{2})-(-x^{2}y^{2}+7-8xy^{2}+2y^{2})$ Remove the grouping symbols. To remove the second parentheses, change the sign of every term inside it: $5x^{2}y^{2}+3-9x^{2}y+y^{2}+x^{2}y^{2}-7+8xy^{2}-2y^{2}=...$ Simplify by combining like terms: $...=(5+1)x^{2}y^{2}-9x^{2}y+8xy^{2}+(1-2)y^{2}+(3-7)=...$ $...=6x^{2}y^{2}-9x^{2}y+8xy^{2}-y^{2}-4$