Question

giúp em với :3

Answer 1

a) \(x^2-3x=0\)

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

⇔\(\left[{}\begin{matrix}x=0\\x-3=0\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)

b) \(5x^3-15x^2=0\)

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

⇔\(\left[{}\begin{matrix}5x^2=0\\x-3=0\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)

Answer 2

\(a,\Rightarrow x\left(x-3\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\\ b,\Rightarrow2x\left(1-2x\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{2}\end{matrix}\right.\\ c,\Rightarrow5x^2\left(x-3\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\\ d,\Rightarrow x\left(x^2-9\right)=0\\ \Rightarrow x\left(x-3\right)\left(x+3\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x=3\\x=-3\end{matrix}\right.\)

Answer 3

c) \(2x-4x^2=0\)

\(2x\left(1-2x\right)=0\)

⇔\(\left[{}\begin{matrix}2x=0\\1-2x=0\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}x=0\\x=\dfrac{1}{2}\end{matrix}\right.\)

d) \(x^3-9x=0\)

\(x\left(x^2-9\right)=0\)

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

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

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

⇔\(\left[{}\begin{matrix}x=0\\x=-3\\x=3\end{matrix}\right.\)