\(2x^2-1=49\)
\(2x^2=49+1\)
\(2x^2=50\)
\(x^2=50:2\)
\(x^2=25\)
\(\Rightarrow\left\{{}\begin{matrix}x^2=5^2\\x^2=\left(-5\right)^2\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x=5\\x=-5\end{matrix}\right.\) \(\left(TM\right)\)
Vậy \(x\in\left\{5;-5\right\}\) là giá trị cần tìm
