Tìm gía trị của x, biết: 
a. x(8x - 2) - 8x^2 + 12 = 0
<=> (8x^2 - 2x) - 8x^2 + 12 = 0
<=> 8x^2 - 2x - 8x^2 + 12 = 0
<=> (8x^2 - 8x^2) - 2x + 12 = 0
<=> 0 + 12 - 2x = 0
<=> 12 - 2x = 0
<=> 2x = 12
<=> x = 12 : 2
<=> x = 6
Vậy x = 6
 

b. x(4x - 5) - (2x - 1)^2 = 0
<=> (4x^2 - 5x) - (4x^2 - 4x + 1) = 0
<=> 4x^2 - 5x - 4x^2 + 4x - 1 = 0
<=> (4x^2 - 4x^2) + (4x - 5x) - 1 = 0
​<=> 0 + (-x) - 1 = 0
<=> - x - 1 = 0
<=> -x = 1
<=> x = -1
Vậy x = -1