\(a.\)
\(2x^2+0.82=1\)
\(\Rightarrow2x^2+0=1\)
\(\Rightarrow2x^2=1\)
\(\Rightarrow x^2=\dfrac{1}{2}\)
\(\Rightarrow x=\pm\sqrt{\dfrac{1}{2}}\)
\(b.\)
\(4x^2-1=0\)
\(4x^2=1\)
\(\Rightarrow x^2=\dfrac{1}{4}\)
\(\Rightarrow x=\pm\sqrt{\dfrac{1}{4}}=\pm\dfrac{1}{2}\)
\(c.\)
\(\left(3x-\dfrac{1}{4}\right)\left(x+\dfrac{1}{2}\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}3x-\dfrac{1}{4}=0\\x+\dfrac{1}{2}=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}3x=\dfrac{1}{4}\\x=-\dfrac{1}{2}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{12}\\x=-\dfrac{1}{2}\end{matrix}\right.\)