`(2x - 1)^4 = 81`
`=> (2x - 1)^4 = 3^4`
`=> 2x - 1 = (+-3)`
`=>`\(\left[ \begin{array}{l}2x - 1 = -3 \\2x - 1 = 3\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x = (-3) + 1\\2x = 3 + 1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x = -2\\2x = 4\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=-1\\x=2\end{array} \right.\)
Vậy `x in {-1; 2}`
`5^x + 5^{x + 2} = 650`
`<=> 5^x . 1 + 5^x . 5^2 = 650`
`<=> 5^x(1 + 5^2) = 650`
`<=> 5^x(1 + 25) = 650`
`<=> 5^x . 26 = 650`
`<=> 5^x = 650 : 26`
`<=> 5^x = 25`
`<=> 5^x = 5^2`
`<=> x = 2`
Vậy `x = 2`
`(x - 1)^5 = -32`
`=> (x - 1)^5 = (-2)^5`
`=> x - 1 = -2`
`=> x = (-2) + 1`
`=> x = -1`
Vậy `x = -1`
