Answer
$y=2|x-5|+2$.
Work Step by Step
The absolute value functions have the form $y=a|x-b|+c$ where $(b,c)$ is the vertex of the function.
Hence here because the vertex is at $(5,2)$, $y=a|x-5|+2$.
Since $(4,4)$ is on the function, plugging in the values we get: $4=a|4-5|+2\\2=a$.
Thus $y=2|x-5|+2$.