Simplify 5x^2+14y-9y+x^2-7x^2-y

$5 x^{2} + 14 y - 9 y + x^{2} - 7 x^{2} - y$

Add $5 x^{2}$ and $x^{2}$ .

$6 x^{2} + 14 y - 9 y - 7 x^{2} - y$

Subtract $7 x^{2}$ from $6 x^{2}$ .

$- x^{2} + 14 y - 9 y - y$

Subtract $9 y$ from $14 y$ .

$- x^{2} + 5 y - y$

Subtract $y$ from $5 y$ .

$- x^{2} + 4 y$