Question

tìm x, biết:

(4x + 1)(-x - 9) = 0

Answer 1

`(4x+1)(-x-9)=0`

\(< =>\left[{}\begin{matrix}4x+1=0\\-x-9=0\end{matrix}\right.\\ < =>\left[{}\begin{matrix}4x=-1\\-x=9\end{matrix}\right.\\ < =>\left[{}\begin{matrix}x=-\dfrac{1}{4}\\x=-9\end{matrix}\right.\)

Answer 2

`(4x+1)(-x-9)=0`

TH1: `4x+1=0`

`=>4x=-1`

`=>x=-1/4`

TH2: `-x-9=0`

`=>-x=9`

`=>x=-9`

Vậy `x\in{-1/4;-9}`