a, | 2x - 1 | = 5
⇒ \(\left[{}\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\)
⇒ \(\left[{}\begin{matrix}2x=6\\2x=-4\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)
Vậy \(x\in\left\{3;-2\right\}\)
b) \(\left(5^x-1\right).3-2=70\)
⇒ \(\left(5^x-1\right).3=72\)
⇒ 5x - 1 = 24
⇒ \(5^x=25\)
\(\Rightarrow5^x=5^2\)
\(\Rightarrow x=2\)
Vậy x = 2
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#Chiyuki Fujito