3) `(2x - 1)^2 = 1 - 2x`
`=>`\(\left[ \begin{array}{l}2x - 1 = 1 - 2x \\2x - 1 = 2x - 1\end{array} \right.\) `=>`\(\left[ \begin{array}{l}4x = 2\\0x = 2\end{array} \right.\) `=>`\(\left[ \begin{array}{l}x=0,5\\x ∈ ∅\end{array} \right.\)
Vậy `x = 0,5`.
4) `(5 - x)^2 = 7 (5 - x)`
`=>`\(\left[ \begin{array}{l}5 - x = 35 - 7x\\5 - x = 7x - 35\end{array} \right.\) `=>` \(\left[ \begin{array}{l}6x = 30\\8x = 40\end{array} \right.\) `=> x = 5`
Vậy `x = 5`.
5) `(x - 1/2)^2 + 1/2 = x`
`=> (x - 1/2)^2 - x + 1/2 = 0`
`=> (x - 1/2)^2 - (x - 1/2) = 0`
`=> (x - 1/2) (x - 1/2 - 1) = 0`
`=> (x - 1/2) (x - 3/2) = 0`
`=> x - 1/2 = 0` hoặc `x - 3/2 = 0`
`=> x = 1/2` hoặc `x = 3/2`
Vậy `x ∈ {1/2 ; 3/2}`.
