Respuesta :

Alishameeks
If a ≥ 0 then √a denotes the non negative square root of a.

(x-9)^2 = (-(x-9))^2

So both x−9 and −(x−9) are square roots of (x−9)2, but we want to pick whichever is non negative.

x−9| does that for us.

Answer should be √(x-9)^2) = x-9