`a)(3x-2)(4x+5)=0`
\(\Leftrightarrow\left[{}\begin{matrix}3x-2=0\\4x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=2\\4x=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=\dfrac{-5}{4}\end{matrix}\right.\)
Vậy `x=2/3` hoặc `x=-5/4`
`b)(2,3x-6,9)(0,1x+2)=0`
\(\Leftrightarrow\left[{}\begin{matrix}2,3x-6,9=0\\0,1x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2,3x=6,9\\0,1x=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-20\end{matrix}\right.\)
Vậy `x=3` hoặc `x=-20`
`c)(4x+2)(x^2 +1)=0`
\(\Leftrightarrow\left[{}\begin{matrix}4x+2=0\\x^2+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}4x=-2\\x^2=-1\end{matrix}\right.\Leftrightarrow x=-\dfrac{1}{2}\)
Vậy `x=-1/2`
`d)(2x+7)(x-5)(5x+1)=0`
\(\Leftrightarrow\left[{}\begin{matrix}2x+7=0\\x-5=0\\5x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=-7\\x=5\\5x=-1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-7}{2}\\x=5\\x=\dfrac{-1}{5}\end{matrix}\right.\)
Vậy `x=-7/2` hoặc `x=5` hoặc `x=-1/5`
`e)(x-1)(2x+7)(x^2+2)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\2x+7=0\\x^2+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\2x=-7\\x^2=-2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{7}{2}\end{matrix}\right.\)
Vậy `x=1` hoặc `x=-7/2`
`f)(4x-10)(24+5x)=0`
\(\Leftrightarrow\left[{}\begin{matrix}4x-10=0\\24+5x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}4x=10\\5x=-24\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=\dfrac{-24}{5}\end{matrix}\right.\)
Vậy `x=5/2` hoặc `x=-24/5`
a) \(\left(3x-2\right)\left(4x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}3x-2=0\\4x+5=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{5}{4}\end{matrix}\right.\)
b)\(\left(2.3x-6.9\right)\left(0.1x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2.3x-6.9=0\\0.1x+2=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-20\end{matrix}\right.\)
c) \(\left(4x+2\right)\left(x^2+1\right)=0\)
\(\Leftrightarrow4x+2=0\) (vì \(x^2+1>0\forall m\))
\(\Leftrightarrow x=-\dfrac{1}{2}\)
d) \(\left(2x+7\right)\left(x-5\right)\left(5x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x+7=0\\x-5=0\\5x+1=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{7}{2}\\x=5\\x=-\dfrac{1}{5}\end{matrix}\right.\)
e) \(\left(x-1\right)\left(2x+7\right)\left(x^2+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\2x+7=0\end{matrix}\right.\) (vì \(x^2+2>0\forall m\))
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{7}{2}\end{matrix}\right.\)
f) \(\left(4x-10\right)\left(24+5x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}4x-10=0\\24+5x=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=-\dfrac{24}{5}\end{matrix}\right.\)
