Có: \(h\left(x\right)=3x^2+x=0\)
\(\Leftrightarrow x\left(3x+1\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}x=0\\3x+1=0\end{array}\right.\) \(\Leftrightarrow\left[\begin{array}{nghiempt}x=0\\x=-\frac{1}{3}\end{array}\right.\)
ta có: h(x)=3x2+x=x(3x+1)=0
<=> \(\left[\begin{array}{nghiempt}x=0\\x=-\frac{1}{3}\end{array}\right.\)