Question

tìm x biết :

x^2-9x+20=0

Answer 1

<=>x^2-4x-5x+20=0

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

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

=>x=5; x=4

Answer 2

\(x^2-9x+20=0\)

\(\Leftrightarrow x^2-4x-5x+20=0\)

\(\Leftrightarrow\left(x^2-4x\right)-\left(5x-20\right)=0\)

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

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

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

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

Vậy \(x=4\) hoặc \(x=5\)

Answer 3

x²-9x+20=0

<=>x² - 4x-5x +20 =0

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

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

<=> x-5=0 hoặc x-4=0

<=> x=5 hoặc x=4

Vậy x=5 hoặc x=4