:tìm x 5x(x^2-9)=0 x^2-7x+10=0

`a) 5x(x² - 9) = 0`

`⇔ 5x(x - 3)(x + 3) = 0`

`⇔` $\left[\begin{matrix} 5x=0\\ x-3=0\\ x+3=0\end{matrix}\right.$

`⇔` $\left[\begin{matrix} x=0\\ x=3\\ x=-3\end{matrix}\right.$

Vậy `x ∈ {0;±3}`

`b) x² - 7x + 10 = 0`

`⇔ x² - 5x - 2x + 10 = 0`

`⇔ x(x - 5) - 2(x - 5) = 0`

`⇔ (x - 5)(x - 2) = 0`

`⇔` $\left[\begin{matrix} x-5=0\\ x-2=0\end{matrix}\right.$

`⇔` $\left[\begin{matrix} x=5\\ x=2\end{matrix}\right.$

Vậy `x ∈ {5; 2}`