#### Answer

$(-\infty, 0)$

#### Work Step by Step

Graph
$y_1 =(x+1)^2$ (the orange graph) and
$y_2=(x-1)^2$ (the purple graph)
on the same coordinate plane.
(refer to the attached image below for the graph)
The solution to the given inequality is the set of x-values for which $y_1 \lt y_2$.
Notice that $y_1$ (the orange graph) is less than $y_2$ for x values to the left of $0$.
Thus, the solution to the given inequality is:
$(-\infty, 0)$