`a)`
Cách `1:`
`(x-4)^2 - 16 = 0`
`=> (x-4)^2 = 16`
`=> (x-4)^2= 4^2`
`=> x-4=4` hoặc `x-4=-4`
`+) x - 4 = 4 => x = 8`
`+) x -4 = -4 => x = 0`
Vậy `x \in {8;-0}`
Cách `2:`
`(x-4)^2 - 16 = 0`
`=> (x-4)^2 - 4^2 = 0`
`=> (x-4+4)(x-4-4)= 0`
`=> x (x-8)=0`
`=>x=0` hoặc `x-8=0`
`+) x = 0`
`+) x- 8 =0 => x =8`
Vậy `x \in { 0 ;8}`
`b)`
`(x-3)^2 + (x+3)^2 -2(x+1)(x+2)=0`
`=> (x^2 - 2 . x . 3 + 3^2) + (x^2 + 2 . x . 3 + 3^2) - (2x+2)(x+2) = 0`
`=> (x^2 - 6x+ 9) + (x^2 + 6x+9) - (2x^2 + 4x + 2x + 4) = 0`
`=> x^2 - 6x+ 9 + x^2 + 6x+9 - 2x^2 - 4x - 2x - 4 = 0`
`=> (x^2 + x^2 - 2x^2) + (-6x + 6x -4x-2x) + (9+9-4) = 0`
`=> -6x + 14 =0 `
`=> -6x = -14`
`=> x = 7/3`
Vậy `x=7/3`
