B3) t² (t -3)(t+3) =0;
t² -t²+9 -3t=0;
t=3.
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B4) b^6+27a³ =(b²)³ +(3a)³ = (b²+3a)(b^4 - b²*a +9a²) .
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B5) y³+3y² -y -3 =0;
y²(y+3) -(y+3) =0;
(y+3)(y²-1) =0;
(y+3)(y+1)(y-1)=0;
y₁= - 3 ;
y₂ = - 1;
y₃ = 1.