Question

Tìm x:

x⁴-10x²+9=0

Answer 1

\(\Leftrightarrow x^4-x^2-9x^2+9=0\)

\(\Leftrightarrow x^2\left(x^2-1\right)-9\left(x^2-1\right)=0\)

\(\Leftrightarrow\left(x^2-9\right)\left(x^2-1\right)=0\)

\(\Leftrightarrow\left(x-3\right)\left(x+3\right)\left(x-1\right)\left(x+1\right)=0\)

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

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