Answer
$11x^2-10xy-y^2$
Work Step by Step
Removing the grouping symbols and then combining like terms, the given expression, $
(6x^2-2xy+y^2)+(5x^2-8xy-2y^2)
,$ simplifies to
\begin{array}{l}\require{cancel}
6x^2-2xy+y^2+5x^2-8xy-2y^2
\\\\=
(6x^2+5x^2)+(-2xy-8xy)+(y^2-2y^2)
\\\\=
11x^2-10xy-y^2
.\end{array}