Question

Answer 1

\(18.x^2+6x+8=-1\)

\(\Leftrightarrow x^2+6x+8+1=0\)

\(\Rightarrow x^2+6x+9=0\)

\(\left(a=1;b=3;c=9\right)\)

\(\Delta'=b'^2-ac\)

    \(=3^2-1.9\)

    \(=0=0\)

Vậy phương trình có 1 nghiệm kép

\(x_1=x_2=\dfrac{-b}{a}=\dfrac{-3}{1}=-3\)

Vậy....

Answer 2

`18)`

`x^2 + 6x+8=-1`

`<=>x^2 + 6x + 9=0`

`<=>x^2 + 2.3x+3^2=0`

`<=>(x+3)^2=0`

`<=>x+3=0`

`<=>x=-3`

Vậy `x=-3`

Answer 3

Answer 4

`18)`

`x^2 - 6x+8=-1`

`<=>x^2 - 6x + 9=0`

`<=>x^2 - 2.3x+3^2=0`

`<=>(x-3)^2=0`

`<=>x-3=0`

`<=>x=3`

Vậy `x=3`