a) 5(x-1)(x+1)=5x^2+3x-2
<=> (5x-5)(x+1) = (x+1)(5x-2)
<=> (x+1)(5x-5) - (x+1)(5x-2)=0
<=> (x+1)(5x-5-5x+2)=0
<=> (x+1).(-3)=0
<=> x+1=0<=> x=-1
b) 6 - |2x-1|=3
<=> |2x-1|=3
<=> 2x-1=3 hoặc 2x-1=-3
TH1: 2x-1=3 <=>2x=4<=> x=2
TH2: 2x-1=-3 <=> 2x=-2 <=> x=-1