a)x - 4 + 2x = 4 - x <=> 4x = 8 <=> x = 2
b)2x + 3/4 = 1 + x - 7/5 <=> 2x + 3/4 = x - 2/5
<=> 10x + 15 = 4x - 8 <=> 6x = -23 <=> x = -23/6
c)(3x - 36)(1 - 2x)(x + 1) = 0
<=> 3x - 36 = 0 hoặc 1 - 2x = 0 hoặc x + 1 = 0
<=> x = 12 hoặc x = 1/2 hoặc x = -1
d)x^2 - 5x + 4 = x^2 - x - 4x + 4 = 0
<=> x(x - 1) - 4(x - 1) = 0
<=> (x - 4)(x - 1) = 0 <=> x = 4 hoặc x = 1