\[2x \cdot \left( 3x^{2} + 5xy - y^{2} \right) =\]
\[= 2x \cdot 3x^{2} + 2x \cdot 5xy - 2x \cdot y^{2} =\]
\[= 6x^{3} + 10x^{2}y - 2xy^{2}\text{.\ }\]