Answer
$(5y^4 - 7y^2 + x^2 - 3) + (- 3y^4 + 2y^2 + 4)$
$= 2y^4 - 5y^2 + x^2 + 1$
Work Step by Step
$(5y^4 - 7y^2 + x^2 - 3) + (- 3y^4 + 2y^2 + 4)$
$= 5y^4 - 3y^4 - 7y^2 + 2y^2 + x^2 - 3 + 4$ (Group like terms)
$= 2y^4 - 5y^2 + x^2 + 1$ (Combine like terms)