Question

tìm x thuộc z biết :

(x²+4)(x²-16) < 0 

nhanh mk tk nha!

Answer 1

\(\left(x^2+4\right)\left(x^2-16\right)< 0\)

\(\Rightarrow\hept{\begin{cases}x^2+4>0;x^2-16< 0\\x^2+4< 0;x^2-16>0\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x^2>-4;x^2< 16\\x^2< -4;x^2>16\end{cases}}\)

\(\Rightarrow-4< x^2< 16\)

Answer 2

\(\Rightarrow x\in\left\{1;4;9\right\}.\)