1) \(3x(x^2-4)=0 \)

\(=> 3x(x-2)(x+2)=0\)

\(=>\left[\begin{array}{nghiempt}3x=0\\x-2=0\\x+2=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=2\\x=-2\end{array}\right.\)

Vậy \(x\in\left\{0;2;-2\right\}\)

2) \(2x^2-x-6=0\)

\(2x^2-4x+3x-6=0\)

\(\left(2x^2-4x\right)+\left(3x-6\right)=0\)

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

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

\(\Rightarrow\left[\begin{array}{nghiempt}x-2=0\\2x+3=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=2\\x=-\frac{3}{2}\end{array}\right.\)

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

\(a^3b+ab^3+2a^2b+2a+2b+1=0\)

Cmr \(1-ab\) là bình phương của một số hữu tỉ