a/

\(\left(1-3x\right)^3=\left(-4\right)^3\Leftrightarrow1-3x=-4\Leftrightarrow x=\frac{5}{3}\)

b/

\(\left(4-3x\right)^4=\left(4-3x\right)^2\Leftrightarrow\left(4-3x\right)^2\left[\left(4-3x\right)^2-1\right]=0\)

\(\Leftrightarrow\left(4-3x\right)^2\left(5-3x\right)\left(3-3x\right)=0\)

\(\Leftrightarrow3-3x=0\) hoặc \(4-3x=0\) hoặc \(5-3x=0\)

\(\Leftrightarrow x=1\) hoặc \(x=\frac{4}{3}\) hoặc \(x=\frac{5}{3}\)

c/

\(\frac{7^{x+2}+7^{x+1}+7^x}{57}=\frac{5^{2x}+5^{2x+1}+5^{2x+3}}{131}\)\(\Leftrightarrow\frac{49.7^x+7.7^x+7^x}{57}=\frac{5^{2x}+5.5^{2x}+125.5^{2x}}{131}\)

\(\Leftrightarrow7^x=5^{2x}\Leftrightarrow7^x=25^x\Leftrightarrow\left(\frac{7}{25}\right)^x=1=\left(\frac{7}{25}\right)^0\)

\(\Rightarrow x=0\)