`15,4(x-5)=5-x`
`<=>4x-20-5+x=0`
`<=>5x-25=0`
`<=>5x=25`
`<=>x=5`
`16) x^2 – 3x = 4(x – 3)`
`<=>x^2-3x-4x+12=0`
`<=>x^2-x+12=0`
`<=>x^2-4x-3x+12=0`
`<=>(x-4)(x-3)=0`
`<=>x=4` hoặc `x=3`
`17,x^2 - x - (3x - 3) = 0`
`<=>x^2-x-3x+3=0`
`<=>x^2-4x+3=0`
`<=>(x-3)(x-1)=0`
`<=>x=3` hoặc `x=1`
`18) (x – 3)^2 = –x + 3`
`<=>x^2-6x+9=3-x`
`<=>x^2-5x+6=0`
`<=>(x-3)(x-2)=0`
`<=>x=3` hoặc `x=2`
`19, (x – 2)^2 – x + 2 = 0`
`<=>x^2-5x+6=0`
`<=>(x-3)(x-2)=0`
`<=>x=3` hoặc `x=2`
`20) (2x – 3)^2 = 2x – 3`
`<=>4x^2-12x+9-2x+3=0`
`<=>2(2x^2-7x+6)=0`
`<=>2(2x-3)(x-2)=0`
`<=>x=3/2` hoặc `x=2`
`21) (2x –1)^2 + (2 –x)(2x –1) = 0`
`<=>(2x-1)(2x-1+2x-x)=0`
`<=>(2x-1)(x+1)=0`
`<=>x=1/2` hoặc `x=-1`
`22) (3x + 4)(x – 4) = (x – 4)^2`
`<=>3x^2-8x-16=x^2-8x+16`
`<=>3x^2-x^2=32`
`<=>x^2=16`
`<=>x=+-4`
Vậy ............
