a) \(-\frac{1}{2}\times\sqrt{2x+1}=-\frac{3}{4}\)
\(\sqrt{2x+1}=\frac{-3}{4}:\frac{-1}{2}\)
\(\sqrt{2x+1}=\frac{3}{2}\)
\(\left(\sqrt{2x+1}\right)^2=\frac{9}{4}\)
\(2x+1=\frac{9}{4}\)
\(2x=\frac{9}{4}-1\)
\(2x=\frac{5}{4}\)
\(x=\frac{5}{4}:2\)
\(x=\frac{5}{8}\)