Question

tìm x biết: 20x - 4x² = 0

Answer 1

 `20x - 4x^2=0`

`<=>4x(5-x)=0`

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

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

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

Vậy `x ∈ { 0; 5 }`

Answer 2

20x - 4x² = 0

4x( 5 - x ) = 0

TH1: 4x = 0

           x = 0 : 4

           x = 0

TH2: 5 - x = 0

              x = 5 - 0

              x = 5

Vậy x ∈ { 0; 5 }

Answer 3

4x2−20x=0

4x(x−5)=0

x=0

x−5=0

x=0

x=5