Bài 4:
a) (x-2)^2 - (x-3)(x+3) = 6
<=> x^2 - 4x + 4 - x^2 + 9 = 6
<=> 4x = 7
<=> x = 7/4
b) 4(x-3)^2 -(2x-1)(2x+1) = 10
<=> 4x^2 - 24x + 36 - 4x^2 + 1 = 10
<=> 24x = 27
<=> x = 9/8
Bài 5:
a) 1-2y+y^2 = ( y-1 )^2
b) (x+1)^2 - 25 = (x-4)(x+6)
c) 1-4x^2 = (1-2x)(1+2x)