Đáp án+Giải thích các bước giải:
`A=(5-sqrt5)/(sqrt5-1)-4/(sqrt5+1)`
`=(sqrt5(sqrt5-1))/(sqrt5-1)-((sqrt5-1)(sqrt5+1))/(sqrt5+1)`
`=sqrt5-(sqrt5-1)`
`=sqrt5-sqrt5+1=1.`
`B=(x+sqrtx)/sqrtx+(x-4)/(sqrtx+2)(x>0)`
`=(sqrtx(sqrtx+1))/sqrtx+((sqrtx-2)(sqrtx+2))/(sqrtx+2)`
`=sqrtx+1+sqrtx-2`
`=2sqrtx-1.`