\[\boxed{\text{685.}\text{\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ \frac{(2x + 1)(2x - 3)}{4} =\]
\[= x^{2} - 1\ \ \ | \cdot 4\]
\[4x^{2} + 2x - 6x - 3 = 4x^{2} - 4\]
\[- 4x = - 4 + 3\]
\[- 4x = - 1\]
\[x = \frac{1}{4} = 0,25.\]
\[Ответ:x = 0,25.\]
\[\textbf{б)}\ x^{2} - \frac{(2x - 1)x}{2} = 2\ \ \ \ | \cdot 2\]
\[2x^{2} - 2x^{2} + x = 4\]
\[x = 4.\]
\[Ответ:x = 4.\]