Answer
$(-\infty, -1] \cup [6, +\infty)$
Work Step by Step
The equation involves only the variable x.
Notice that the value of $x^2-4x$ (which is represented by the parabola) is greater than or equal to the value of $x+6$ (which is represented by the line) in the following intervals:
$(-\infty, -1]$
$[6, +\infty)$
Therefore, the solution to the given inequality is:
$(-\infty, -1] \cup [6, +\infty)$