Bài `1:`

`a) x(x-2)=0`

`<=> [(x=0),(x-2=0):}`

`<=>[(x=0),(x=2):}`

Vậy `S={0;2}`

`b) (2x+1)(3x-2)=0`

`<=>[(2x+1=0),(3x-2=0):}`

`<=>[(2x=-1),(3x=2):}`

`<=>[(x=(-1)/2),(x=2/3):}`

Vậy `S={-1/2;2/3}`

`c) (x^2-4)+x(x-2)=0`

`<=> (x-2)(x+2) + x(x-2)=0`

`<=> (x-2)(2x+2)=0`

`<=>[(x-2=0),(2x+2=0):}`

`<=>[(x=2),(x=-1):}`

Vậy `S={2;-1}`

`d) (2x+1)^2 - 9x^2=0`

`<=>4x^2 + 4x + 1 - 9x^2 = 0`

`<=>-5x^2 + 4x + 1 = 0`

`<=>(x-1)(x+1/5)=0`

`<=>[(x-1=0),(x+1/5=0):}`

`<=>[(x=1),(x=-1/5):}`

Vậy `S={1;-1/5}`

Bài `2:`

`a) 5x(2x-3)=0`

`<=> [(5x=0),(2x-3=0):}`

`<=>[(x=0),(2x=3):}`

`<=>[(x=0),(x=3/2):}`

Vậy `S={0;3/2}`

`b) (2x-5)(3x+6)=0`

`<=>[(2x-5=0),(3x+6=0):}`

`<=>[(2x=5),(3x=-6):}`

`<=>[(x=5/2),(x=-2):}`

Vậy `S={5/2;-2}`