Question

√(4x^2-28x+49)=7

 

Answer 1

=>|2x-7|=7

=>2x-7=7 hoặc 2x-7=-7

=>x=7 hoặc x=0

Answer 2

<=>√(2X-7)^2=7

<=>|2X-7|=7

<=>2X-7=7

<=>2X=7+7

=>X=7

Hoặc 2X-7=-7

<=>2X=0

=>X=0

Answer 3

`\sqrt{4x^2-28x+49} =7`

`<=> \sqrt{(2x)^2 - 2.7.2x +7^2} = 7`

`<=> \sqrt{(2x-7)^2} = 7`

`=> |2x-7| = 7`

\(\Leftrightarrow\left[{}\begin{matrix}2x-7=7\\2x-7=-7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=14\\2x=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=7\\x=0\end{matrix}\right.\)