Bài 1:
a) 9/4x^2+3x+4 = (3/2x)^2 + 2(3/2x) + 4
b) (9x^2+12x+4)+6(3x+2)+9 = (3x+2)^2 + 3(3x+2) + 1
c) 9x^2+4y^2+2(3x+2y+6xy)+1 = (3x+2y+1)^2

Bài 2:
a) 3(x-1)^2-3x(x-5)=1
=> 3x^2 - 24x + 36 = 1
=> 3x^2 - 24x + 35 = 0
=> x = 5/3 hoặc x = 7/3
b) (6x-2)^2+(5x-2)^2-4(3x-1)(5x-2)=0
=> 61x^2 - 124x + 60 = 0
=> x = 2/5 hoặc x = 6/5

Bài 3:
a) (2x+5)(2x-5) = 4x^2 - 25
b) (x^2+3)(3-x^2) = 3 - x^4
c) 3x(x-1)^2-2x(x+3)(x-3)+4x(x-4) = -2x^3 + 29x^2 - 38x
d) 4(2x+5)^2-2(3x+1)(1-3x) = 32x^2 + 56x + 22