Question

Tìm x biết : (x-4)(5x-2)-3(4-x)=0

Answer 1

\(\left(x-4\right)\left(5x-2\right)-3\left(4-x\right)=0\)

\(\Leftrightarrow\left(x-4\right)\left(5x-2\right)+3\left(x-4\right)=0\)

\(\Leftrightarrow\left(x-4\right)\left(5x-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-4=0\\5x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\5x=2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=\dfrac{2}{5}\end{matrix}\right.\)

Answer 2

\(\left(x-4\right)\left(5x-2\right)-3\left(4-x\right)=0\Leftrightarrow\left(x-4\right)\left(5x-2\right)+3\left(x-4\right)=0\)

\(\Leftrightarrow\left(5x-2+3\right)\left(x-4\right)=0\Leftrightarrow\left(5x+1\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}5x+1=0\\x-4=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}5x=-1\\x=4\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{5}\\x=4\end{matrix}\right.\) vậy \(x=\dfrac{-1}{5};x=4\)