Question

giải phương trình: -x^4-2x^2+8=0

 

Answer 1

\(-x^4-2x^2+8=0\\ \Leftrightarrow x^4+2x^2-8=0\\ \Leftrightarrow\left(x^4-2x^2\right)+\left(4x^2-8\right)=0\\ \Leftrightarrow x^2\left(x^2-2\right)+4\left(x^2-2\right)=0\\ \Leftrightarrow\left(x^2-2\right)\left(x^2+4\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x^2=2\\x^2=-4\left(vô.lí\right)\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\sqrt{2}\\x=-\sqrt{2}\end{matrix}\right.\)