P(x)=0 <=> ||x+3|+5|-2023 = 0
<=> ||x+3|+5| = 2023
<=>\(\left[\begin{array}{nghiempt}\left|x+3\right|+5=2023\\\left|x+3\right|+5=-2023\end{array}\right.\) <=> \(\left[\begin{array}{nghiempt}\left|x+3\right|=2018\\\left|x+3\right|=-2028\end{array}\right.\) <=> |x+3| = 2018 (vì |a| \(\ge\) 0)
<=> \(\left[\begin{array}{nghiempt}x+3=2018\\x+3=-2018\end{array}\right.\) <=> \(\left[\begin{array}{nghiempt}x=2015\\x=-2021\end{array}\right.\)
Vậy x1 = 2015 và x2 = -2021 là nghiệm của đa thức P(x)