Question

Tìm x :

\(x^3+2\sqrt{2}x^2+2x=0\)

Answer 1

\(x^3+2\sqrt{2}x^2+2x=0\)

\(x\left(x^2+2\sqrt{2}x+2\right)=0\)

\(x\left(x+\sqrt{2}\right)^2=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\\left(x+\sqrt{2}\right)^2=0\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\x=-\sqrt{2}\end{cases}}\)

Vậy \(S=\left\{0;-\sqrt{2}\right\}\)

Answer 2

\(x^3+2\sqrt{2}x^2+2x=0\)

\(x\left(x+2\cdot x\sqrt{2}+2\right)=0\)

\(x\left(x+\sqrt{2}\right)^2=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\\left(x+\sqrt{2}\right)^2=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=-\sqrt{2}\end{cases}}\)

Vậy ....