Answer
-y$^3$+8y$^2$+y+14
Work Step by Step
Distribute the negative sign to the parentheses and then combine like terms vertically.
$\quad5y^3+6y^2-3y+10$
$\underline{-(6y^3-2y^2-4y-4)}$
$\qquad\qquad\downarrow$
$\quad5y^3+6y^2-3y+10$
$\underline{-\;6y^3+2y^2+4y+4}$
$\quad-y^3+8y^2+y+14$
