a) (3x-1)(2x-5)=(3x-1)(x+4)
⇔6x²-15x-2x+5 = 3x²+12x-x-4
⇔3x²-28x+9 = 0
⇔(3x-1)(x-9)=0
⇔3x-1=0 ⇔ x=1/3
x-9=0 ⇔ x=9
vậy S={ 1/3 ; 9 }
b) x-2/4 - 3x-1/3 = x-25/6
⇒3(x-2) - 4(3x-1) = 2(x-25)
⇔3x-6 - 12x + 4 = 2x-50
⇔-9x-2 = 2x-50
⇔ -11x + 48=0
⇔ x = 48/11
c) x+2/x-2 -1/x = 2/x²-2x
⇔x+2/x-2 -1/x = 2/x(x-2)
⇒ (x+2)x - x+2 = 2
⇔x²+2x - x+2 =2
⇔x²+x+2-2=0
⇔x²+x=0
⇔x(x+1)=0
⇔ x+1=0 ⇔ x=⇔-1