Chapter 4 - Section 4.2 - Adding and Subtracting Polynomials - 4.2 Exercises - Page 286: 83

$y^4-4y^2-4$

Removing the grouping symbols and then combining like terms, the given expression, $ [-(y^4-y^2+1)-(y^4+2y^2+1)]+(3y^4-3y^2-2) ,$ simplifies to \begin{array}{l}\require{cancel} [-y^4+y^2-1-y^4-2y^2-1]+3y^4-3y^2-2 \\\\= -y^4+y^2-1-y^4-2y^2-1+3y^4-3y^2-2 \\\\= (-y^4+3y^4-y^4)+(y^2-2y^2-3y^2)+(-1-1-2) \\\\= y^4-4y^2-4 .\end{array}