Given $\displaystyle f(x) = 3 - x - x^2$, find equation of $\displaystyle -f(x)$

The teacher didn't like my answer, what's wrong with the way I wrote this?

$\displaystyle f(x) = 3 - x - x^2$

$\displaystyle f(x) = -(3 - x - x^2)$

$\displaystyle f(x) = -3 - (-x) - (-x^2)$

$\displaystyle f(x) = -3 + x - x^2$

I don't know what I did wrong...

edit: I meant -f(x)