a: ĐKXĐ: x>=0
\(\left(x^3-\frac{27}{64}\right)\left(\sqrt{x}-3\right)=0\)
=>\(\left[\begin{array}{l}x^3-\frac{27}{64}=0\\ \sqrt{x}-3=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x^3=\frac{27}{64}\\ \sqrt{x}=3\end{array}\right.\Rightarrow\left[\begin{array}{l}x=\frac34\left(nhận\right)\\ x=9\left(nhận\right)\end{array}\right.\)
b: \(\left(\frac12-\frac47x\right)^3=-\frac{8}{343}\)
=>\(\left(\frac12-\frac47x\right)^3=\left(-\frac27\right)^3\)
=>\(\frac12-\frac47x=-\frac27\)
=>\(\frac47x=\frac12+\frac27=\frac{7+4}{14}=\frac{11}{14}\)
=>\(x=\frac{11}{14}:\frac47=\frac{11}{14}\cdot\frac74=\frac{11}{2\cdot4}=\frac{11}{8}\)
