Answer
$$
0=(0,0,0).
$$
$$-u=(-a,-b,-c).$$
Work Step by Step
The zero vector of the vector space $R^3$ is given by
$$
0=(0,0,0).
$$
Let $u$ be an vector in $R^3$ such that
$$u=(a,b,c).$$
Now, the additive inverse of $u$ is given by
$$-u=(-a,-b,-c).$$