Subpunctele a,b,c .. frumos explicate. Mulțumesc anticipat !

a) f(x)=x³ + x² + x+1
0=x³ + x² + x + 1
0-x³ -x² - x -1 =0
-x² ori (x+1)-(x+1)=0
(x+1) ori (x²+1)=0
x1=0
x²+1=0
x = -1