16:
a: =>(x-5)(x^2-1)=0
=>(x-5)(x+1)(x-1)=0
=>\(x\in\left\{5;-1;1\right\}\)
b: =>3x^3(x-3)=-9x(x-3)
=>(x-3)(3x^3+9x)=0
=>3x(x^2+3)(x-3)=0
=>x(x-3)=0
=>x=0 hoặc x=3
c: =>(x+8)*x^2+x(x+8)=0
=>x(x+8)(x+1)=0
=>\(x\in\left\{0;-1;-8\right\}\)
d: =>(x+3)(x^2-3x+5-x)=0
=>x+3=0
=>x=-3