x³ =t ⇒ t² -9 t +8 =0 t₁ =1 t₂=8
x³=1 x³ -1=0 (x-1)·( x² +x +1) =0 ⇒ radacina x=1
↓ Δ<0 radacini complexe
x³=8 x³-2³=0 ( x-2) ( x² +2x+4 ) =0 ⇒ radacina x=2
↓ Δ< radacini complexe
x⁴ -29x² +100=0
x² =t
t² -29t +100=0 t₁=4 si t₂=25
x²=4 radacini x₁=2 x₂=-2
x²=25 x₃=5 x₄=-5