Simplify 2x^2-3xy+4y^2-3x^2-5xy-6y^2

$2 x^{2} - 3 x y + 4 y^{2} - 3 x^{2} - 5 x y - 6 y^{2}$

Subtract $3 x^{2}$ from $2 x^{2}$ .

$- x^{2} - 3 x y + 4 y^{2} - 5 x y - 6 y^{2}$

Subtract $5 x y$ from $- 3 x y$ .

$- x^{2} + 4 y^{2} - 8 x y - 6 y^{2}$

Subtract $6 y^{2}$ from $4 y^{2}$ .

$- x^{2} - 2 y^{2} - 8 x y$