Giải thích các bước giải:
`d, \ (asqrta+bsqrtb)/(sqrta+sqrtb)-(sqrta-sqrtb)^2`
`=((sqrta+sqrtb)(a+sqrt(ab)+b))/(sqrta+sqrtb)-(a-2sqrt(ab)+b)`
`=a+sqrt(ab)+b-a+2sqrt(ab)-b`
`=3sqrt(ab)`
`d, \ (x+sqrt(xy))/(y+sqrt(xy)) qquad (x>=0 ; y>0)`
`=(sqrtx(sqrtx+sqrty))/(sqrty(sqrty+sqrtx))=(sqrtx)/(sqrty)`