Short answer 4 units to the right.
Remark
Graph the two equations.
The purple graph is y = x^2
The black graph is y = (x - 4)^2
Rule
1. When a constant is inside the brackets, the graph moves left or right. To tell which use the second part of the rule.
2. use y = (x + a)^2 as your example.
if a > 0 the graph moves left.
if a < 0 then graph moves right.
Just the opposite of what you would expect.
