x^3-9x=0 <=>x(x^2 – 9)=0 TH1:x=0 TH2:(x^2-9)=0 <=>(x^2-3^2)=0 <=>(x-3)(x+3)=0 <=>x-3=0 => x=3 <=>x+3=0 => x=-3 Vậy x=0;x=3;x=-3 Bình luận
x^3-9x=0 x(x^2+9)=0 x(x^2+3^2) x(x+3)(x-3) => x=3 => x+3=0 =>x=-3 => x-3=0 => x=3 => x ∈ (0; 3; -3) Bình luận
x^3-9x=0
<=>x(x^2 – 9)=0
TH1:x=0
TH2:(x^2-9)=0
<=>(x^2-3^2)=0
<=>(x-3)(x+3)=0
<=>x-3=0 => x=3
<=>x+3=0 => x=-3
Vậy x=0;x=3;x=-3
x^3-9x=0
x(x^2+9)=0
x(x^2+3^2)
x(x+3)(x-3)
=> x=3
=> x+3=0 =>x=-3
=> x-3=0 => x=3
=> x ∈ (0; 3; -3)