a: \(\Leftrightarrow5\cdot6^x=180\)
\(\Leftrightarrow6^x=36\)
=>x=2
b: \(\Leftrightarrow x^2\left(x^{18}-1\right)=0\)
hay \(x\in\left\{0;1;-1\right\}\)
c: \(\Leftrightarrow\left(x-1\right)^3\cdot\left[\left(x-1\right)^{17}-1\right]=0\)
=>x-1=0 hoặc x-1=1
=>x=2 hoặc x=1