`1.`
`(2x - 1)^2 = 5^4`
`=> (2x - 1)^2 = (5^2)^2`
`=> (2x - 1)^2 = 25^2`
`=>` \(\left[ \begin{array}{l}(2x - 1)^2 - 25^2\\x=(2x - 1)^2 = (-25)^2\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x - 1 = 25\\2x - 1 = -25\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x =26\\2x = -24\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=13\\x=-12\end{array} \right.\)
Vậy `x ∈ {13 ; -12}`
`2.`
`x^20 + 5^4 = 625`
`=> x^20 + 625 = 625`
`=> x^20 = 625 - 625`
`=> x^20 = 0`
`=> x^20 = 0`
Vậy `x = 0`
