Question

Tìm x

\(x^2+6x=34\)

Answer 1

\(\Leftrightarrow x^2+6x+9=43\)

\(\Leftrightarrow\left(x+3\right)^2=43\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{43}-3\\x=-\sqrt{43}-3\end{matrix}\right.\)

Answer 2

`x^2+6x=34`

`<=>x^2+6x+9=43`

`<=>(x+3)^2=(\sqrt(43))^2`

`<=> [(x+3=\sqrt(43)),(x+3=-\sqrt(43)):}`

`<=> [(x=-3+\sqrt(43)),(x=-3-\sqrt(43)):}`

Vậy `S={-3 +- \sqrt(43)}`.