`- 5x^2 - 9x + 2 = 0 `

2 câu trả lời

`-5x^2 - 9x + 2 = 0`

`-5x^2 - 10x + x + 2 = 0`

`-5x.(x+2)+(x+2)=0`

`(x+2).(-5x+1)=0`

`TH1`

`x+2=0`

`x=-2`

`TH2`

`-5x+1=0`

`-5x=-1`

`x=1/5`

-5x²-9x+2=0

⇔-(5x²+9x-2)=0

⇔-(5x²+10x-x-2)=0

⇔-(5x(x+2)-(x+2))=0

⇔-(5x-1)(x+2)=0

⇔\(\left[ \begin{array}{l}-(5x-1)=0\\x+2=0\end{array} \right.\) 

⇔\(\left[ \begin{array}{l}x=\frac{1}{5} \\x=-2\end{array} \right.\)