Đáp án:
`4(2 - x) + x ( x + 6)= x^2`
`<=> 8 - 4x + x^2 + 6x - x^2 =0`
`<=> 2x + 8 = 0`
`<=> 2x = - 8`
`<=> x= -4`
Vậy `S={ - 4}`
`x(x - 7) - (x -2)( x + 5)= 0`
`<=> x^2 - 7x - x^2 - 3x + 10 = 0`
`<=> -10 x + 10 = 0`
`<=> -10x = -10`
`<=> x = 1`
Vậy `S={ 1}`
`(2x +3)(3 - 2x) + ( 2x - 1)^2 = 2`
`<=> 9 - 4x^2 + 4x^2 - 4x + 1 - 2= 0`
`<=> -4x + 8 = 0`
`<=> -4x = -8`
`<=> x= 2`
Vậy `S={ 2}`
