Question

[thanh bình Nguyễn]

Tìm x biết

3x(x+2)-20x-40=0

6x³+x+4=11x²

Tìm n thuộc z để n³-2 chia hết n-2

Answer 1

[Dương Lam Hàng]

\(3x\left(x+2\right)-20x-40=0\)

\(\Rightarrow3x\left(x+2\right)-20\left(x+2\right)=0\)

\(\Rightarrow\left(3x-2\right)\left(x+2\right)=0\)

\(\Rightarrow\orbr{\begin{cases}3x-2=0\\x+2=0\end{cases}\Rightarrow\orbr{\begin{cases}3x=2\\x=-2\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{2}{3}\\x=-2\end{cases}}}\)

Vậy \(x=\left\{\frac{2}{3};-2\right\}\)