Question

 giải phương trình:

 

 

c) 3x²+13x+12=0

Answer 1

a \(\Leftrightarrow3x^2+9x+4x+12=0\Leftrightarrow3x\left(x+3\right)+4\left(x+3\right)=0\Leftrightarrow\left(x+3\right)\left(3x+4\right)=0\) \(\Leftrightarrow\left[{}\begin{matrix}x+3=0\\3x+4=0\end{matrix}\right.\)  \(\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-\dfrac{4}{3}\end{matrix}\right.\)

Answer 2

\(3x^2+13x+12=0\)

\(\Leftrightarrow3\left(x^2+\dfrac{13}{3}x+4\right)=0\Leftrightarrow x^2+\dfrac{13}{3}x+4=0\)

\(\Leftrightarrow x^2+3x+\dfrac{4}{3}x+4=0\)

\(\Leftrightarrow x\left(x+3\right)+\dfrac{4}{3}\left(x+3\right)=0\)

\(\Leftrightarrow\left(x+\dfrac{4}{3}\right)\left(x+3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{4}{3}\\x=-3\end{matrix}\right.\)