`a)`
`3x^2 - 6x= 0`
`=> 3x (x-2) = 0`
`=>x=0` hoặc `x-2=0`
`+)x=0`
`+)x-2=0=>x=2`
Vậy `x \in {0;2}`
`b)`
`3x^3 -x = 0`
`=> x (3x^2 - 1) = 0`
`=>x=0` hoặc `3x^2 -1=0`
`+)x=0`
`+)3x^2-1=0`
`=> 3x^2 =1`
`=> x^2= 1/3`
`=> x = +-\sqrt{1/3}`
Vậy `x \in {0; \sqrt{1/3} ; - \sqrt{1/3} }`
`c)`
`(x-1)^2 = x+2`
`=> x^2 - 2x + 1 = x+2`
`=> x^2 - 2x + 1 - x - 2=0`
`=> x^2 - 3x - 1 = 0`
`=> (x^2 - 3x + 9/4) - 13/4 = 0`
`=> (x-3/2)^2 = 13/4`
`=> x-3/2 = \sqrt{13/4}` hoặc `x-3/2=- \sqrt{13/4}`
`+)x-3/2= \sqrt{13/4}`
`=> x = (\sqrt{13} + 3)/2`
`+)x-3/2= -\sqrt{13/4}`
`=> x = (-\sqrt{13} + 3)/2`
Vậy `x \in { (\sqrt{13} + 3)/2 ; (-\sqrt{13} + 3)/2 }`
`d)`
`(3x-5)^2- (x+1)^2=0`
`=> [ (3x-5) + (x+1)] . [ (3x-5) - (x+1)] =0`
`=> (3x-5+x+1)(3x-5-x-1)=0`
`=> (4x - 4)(2x-6)=0`
`=> 4x-4=0` hoặc `2x-6=0`
`+) 4x - 4 = 0`
`=> 4x=4`
`=>x=1`
`+)2x-6=0`
`=> 2x=6`
`=>x=3`
Vậy `x \in {1;3}`
`e)`
`(5x-4)^2 - 49x^2 =0`
`=> (5x-4)^2 - (7x)^2 = 0`
`=> (5x-4-7x)(5x-4+7x)=0`
`=> (-2x-4)(12x-4)=0`
`=> -2x-4=0` hoặc `12x-4=0`
`+)-2x-4=0`
`=> -2x = 4`
`=> x= -2`
`+)12x-4=0`
`=> 12x=4`
`=>x=1/3`
Vậy `x \in {-2 ; 1/3}`
