Question

(x²+2x+3)²-9(x²+2x+3)+18=0

Answer 1

Đặt \(x^2+2x+3=t\left(t>0\right)\)

\(\Leftrightarrow t^2-9t+18=0\)

\(\Leftrightarrow t^2-3t-6t+18=0\)

\(\Leftrightarrow\left(t-3\right)\left(t-6\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}t=3\\t=6\end{matrix}\right.\)(TMĐK)

\(\Leftrightarrow\left[{}\begin{matrix}x^2+2x=0\\x^2+2x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=-2\\x=0\end{matrix}\right.\\\left\{{}\begin{matrix}x=1\\x=-3\end{matrix}\right.\end{matrix}\right.\)

Vậy...