a) 3x + 2 chia hết 2x – 1; b) (x- 5) ² . ( 2x – 6 ) < 0

a, 3x+2 $\vdots$2x-1⇒2.(3x+2)$\vdots$2x-1⇒6x+4$\vdots$2x-1⇒3.(2x-1)+7$\vdots$2x-1

⇒2x-1∈Ư(7)={±1;±7}

2x-1=-7⇒2x=-6⇒x=-3

2x-1=-1⇒2x=0⇒x=0

2x-1=1⇒2x=2⇒x=1

2x-1=7⇒2x=8⇒x=4

Vậy x∈{-3;0;1;4}