a, x( x - 1 ) - x² + 2x = 5
x² - x - x² + 2x = 5
2x - x = 5
x( 2 - 1 ) = 5
x = 5
Vậy x = 5
b, 2x² - 2x = ( x - 1 )²
2x² - 2x - ( x - 1 )² = 0
2x( x - 1 ) - ( x - 1 )² = 0
( x - 1 )( 2x - x + 1 ) = 0
( x - 1 )( x + 1) = 0
⇒ x - 1 = 0 hoặc x + 1 = 0
x = 1 x = -1
Vậy x ∈ { 1; -1 }
@maitrang1111