\(a,3^x.3=243\\ \Rightarrow3^x=243:3\\ \Rightarrow3^x=81\\ \Rightarrow3^x=3^4\\ \Rightarrow x=4\\ b,x^{20}=x\\ \Rightarrow x^{20}-x=0\\ \Rightarrow x\left(x^{19}-1\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=0\\x^{19}-1=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\)
\(c,2^x.16^2=1024\\ \Rightarrow2^x=1024:16^2\\ \Rightarrow2x=4\\ \Rightarrow x=4:2=2\)
\(d,64.4^x=16^8\\ \Rightarrow2^6.4^x=\left(2^4\right)^8\\\Rightarrow 4^x=2^{32}:2^6\\ \Rightarrow4^x=2^{26}\\ \Rightarrow4^x=\left(2^2\right)^{13}\\ \Rightarrow4^x=4^{13}\\ \Rightarrow x=13\\ e,2^x.4=128\\ \Rightarrow2^x=128:4\\ \Rightarrow2^x=32\\ \Rightarrow2^x=2^5\\ \Rightarrow x=5\)
@seven
a: =>3^x=81
=>x=4
b: =>x(x^19-1)=0
=>x=0 hoặc x=1
c: =>2^x=1024:256=4
=>x=2
d: =>4^x=4^16:4^3=4^13
=>x=13
e: =>2^x=32
=>x=5
