Question

Tìm x 

a) (x-3)(2x+1)=0

b) 2x(x-5)-x(3+2x)=26

Answer 1

`(x-3)(2x+1)=0`

\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\2x+1=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\2x=-1\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-\dfrac{1}{2}\end{matrix}\right.\)

`----------`

`2x(x-5)-x(3+2x)=26`

`<=> 2x^2 - 10x - 2x - 2x^2=26`

`<=> -13x=26`

`<=>x= -2`

Answer 2

`(x-2).(2x+1)=0`

`=>x-2=0`

`x=0+2`

`x=2`

`=>2x+1=0`

`2x=-1`

`x=-1/2`

____________

`2x.(x-5)-x.(3+2x)=26`

`2x^2-10x-3x-2x^2=26`

`-13x=26`

`x=26:(-13)`

`x=-2`