Question

Answer 1

`(x^2+1)(x^2-1)=0`

`\Leftrightarrow x^4-1=0`

`\Leftrightarrow x^4=1`

`\Leftrightarrow x=\pm1`

Answer 2

`10)`

`(x^2 + 1)(x^2 -1)=0`

`<=>(x^2 +1)(x-1)(x+1)=0`

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

Vậy `x=-1` hoặc `x=1`