vom s tine cont de descompunerea\
a³-b³=(a-b) (a²+ab+b²)
si ca (x+1)(x-2)=x²+x-2x-2=x²-x-2
atunci
| ((x+1-(x-2))(x²+2x+1+(x²-x-2)+x²-4x+4|=9
|3(3x²-3x+3)|=9
|3x²-3x+3|=3
|x²-x+1|=1
x²-x+1=1
x²-x=0
x(x-1)=0
x1=0
x2=1
x²-x+1=-1
x²-x+2=0
Δ=1-8<0
x3,4∉R
S={0;1}
verificare
pt x=0;...|1³-(-8)|=|1+8|=9
pt x=1.... |8-(-1)|=|9|=9
