`a) (x-4)^2 = 5x - 20`

`(x-4)^2 - (5x - 20)=0`

`(x-4)^2 - 5(x-4)=0`

`(x-4)(x-4-5)=0`

`(x-4)(x-9)=0`

`[(x-4=0),(x-9=0):}`

`[(x=4),(x=9):}`

Vậy phương trình đã cho có nghiệm `x = 4` và `x =9`

`b) A = 2sqrt((sqrt3-2)^2) + sqrt12 + 2024`

`= 2|sqrt3 - 2| + sqrt(2^2 . 3) + 2024`

`= 2(2 - sqrt3) + 2sqrt3 + 2024`

`= 4 - 2sqrt3 + 2sqrt3 + 2024`

`= 2028`

`c) ĐKXĐ: x>=0, x\ne4`

`1/(sqrtx - 2) + 1/(sqrtx + 2) - x/(x-4)`

`= (sqrtx+2)/((sqrtx-2)(sqrtx+2)) + (sqrtx-2)/((sqrtx-2)(sqrtx+2)) - x/((sqrtx-2)(sqrtx+2))`

`= (sqrtx + 2 + sqrtx - 2 - x)/((sqrtx-2)(sqrtx+2))`

`= (-x + 2sqrtx)/((sqrtx-2)(sqrtx+2))`

`= (-sqrtx(sqrtx - 2))/((sqrtx-2)(sqrtx+2))`

`= (-sqrtx)/(sqrtx+2)`