`13) x(x-3) -x+3=0`

`<=> x(x-3) -(x-3) =0`

`<=> (x-3)(x-1) =0`

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

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

Vậy `x in {3;1}`

`14) 2x(x-1) -x+1=0`

`<=> 2x(x-1) -(x-1) =0`

`<=> (x-1)(2x-1) =0`

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

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

Vậy `x in {1;1/2}`

`15) x(x+3) -2x-6=0`

`<=> x(x+3)-(2x+6) =0`

`<=> x(x+3) -2(x+3) =0`

`<=> (x+3)(x-2) =0`

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

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

Vậy `x in {-3;2}`

`16) 2x(x+5)-x-5=0`

`<=> 2x(x+5) -(x+5) =0`

`<=> (x+5)(2x-1) =0`

`<=> [(x+5=0),(2x-1=0):}`

`<=> [(x=-5),(x=1/2):}`

Vậy `x in {-5;1/2}`

`17) x(x-3) +2x-6=0`

`<=> x(x-3) +(2x-6) =0`

`<=> x(x-3) +2(x-3) =0`

`<=> (x-3)(x+2) =0`

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

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

Vậy `x in {3;-2}`

`18) x(x-1) +2x-2=0`

`<=> x(x-1) +(2x-2) =0`

`<=> x(x-1) +2(x-1) =0`

`<=> (x-1)(x+2) =0`

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

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

Vậy `x in {1;-2}`

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