\(\left(3x+1\right)^2=25\)
\(\Rightarrow\left(3x+1\right)^2=5^2=\left(-5\right)^2\)
\(\Rightarrow\orbr{\begin{cases}3x+1=5\\3x+1=-5\end{cases}\Rightarrow\orbr{\begin{cases}3x=5-1=4\\3x=-5-1=-6\end{cases}}}\Rightarrow\orbr{\begin{cases}x=\frac{4}{3}\\x=-2\end{cases}}\)
\(\left[x-\frac{1}{2}\right]+\frac{1}{2}=\frac{5}{8}\)
\(\Rightarrow x-0=\frac{5}{8}\)
\(x=\frac{5}{8}\)
\(\left[x+\frac{3}{4}\right]-\frac{1}{3}=0\)
\(x+\frac{3}{4}=0+\frac{1}{3}=\frac{1}{3}\)
\(x=\frac{1}{3}-\frac{3}{4}\)
\(x=\frac{-5}{12}\)
\(\frac{1}{9}.3^4.3x=3^7\)
\(\Rightarrow\frac{1}{9}.3^5x=3^7\)
\(x=3^7:\frac{1}{9}:3^5\)
\(x=3^2.9\)
\(x=81\)
\(\frac{x}{5}=\frac{4}{21}\)
\(\Rightarrow21x=4.5\)
\(\Rightarrow x=\frac{4.5}{21}\)
\(x=\frac{20}{21}\)
