#### Answer

$3$

#### Work Step by Step

RECALL:
The graph of the function $y=f(x)+k$ involves a vertical shift of $|k|$ units (upward when $k$ is positive, downward when $k$ is negative) of the parent function $f(x)$.
The parent function of the given function is $y=x^2$. The given function can be written as $y = f(x) +(-3)$ where $f(x) = x^2$. This equation is of the same same form as the equation in the recall part above with $k=-3$.
Thus, the graph of the given function involves a 3 unit shift downward of its parent function.