ĐKXĐ : `x \ge 0`
`A = 1 : ((x+2sqrtx-2)/(xsqrtx+1)-(sqrtx-1)/(x-sqrtx+1)+1/(sqrtx+1))`
`= 1 : ((x+2sqrtx-2)/((sqrtx+1)(x-sqrtx+1)) - (sqrtx-1)/(x-sqrtx+1) + 1/(sqrtx+1))`
`= 1 : (x+2sqrtx-2-(sqrtx+1)(sqrx-1)+x-sqrtx+1)/((sqrtx+1)(x-sqrtx+1))`
`= 1 : (x+2sqrtx-2-(x-1)+x-sqrtx+1)/((sqrtx+1)(x-sqrtx+1))`
`= 1 : (x+2sqrtx-2-x+1+x-sqrtx+1)/((sqrtx+1)(x-sqrtx+1))`
`= 1 : (sqrtx+x)/((sqrtx+1)(x-sqrtx+1))`
`= 1 : (sqrtx(1+sqrtx))/((sqrtx+1)(x-sqrtx+1))`
`= 1 : sqrtx/(x-sqrtx+1)`
`= (x-sqrtx+1)/sqrtx`
