$\text{Đặt √x=a; }$
$\text{=> a²-3a-10=0; }$
$\text{<=> a²+2a-5a-10=0; }$
$\text{<=> (a+2)(a-5)=0; }$
$\text{<=> \(\left[ \begin{array}{l}a+2=0\\a-5=0\end{array} \right.\) }$
$\text{ <=> \(\left[ \begin{array}{l}a=-2\\a=5\end{array} \right.\) }$
$\text{<=> \(\left[ \begin{array}{l}√x=-2(không thỏa mãn)\\√x=5\end{array} \right.\) }$
$\text{√x=5 }$
$\text{=> x=25 }$
$\text{ }$
