=> 4x2 - 4x + ( x2 + 6x + 9 ) = 9
=> 4x2 - 4x + x2 + 6x + 9 = 9
=> 5x2 + 2x = 0
=> x( 5x + 2 ) = 0
=> x = 0
=> 5x + 2 = 0 => x = -2/5
Vậy x = 0 ; x = -2/5
Tick nha ban... Suy ra 4x^2-4x+x^2+6x+9=9
5x^2+2x+9=9
5x^2+2x=0
X(5x+2)=0
X=0 hoac x=-2/5. Tick di ban