x-8>=0
8-x>=0
∴x=8
把x=8代入Y=根号X-8+根号8-X在加18
得y=18
X-Y/根号X-根号y再减去2xy/x倍根号y-y倍的根号x
=(√x+√y)-2√(xy)/(√x-√y)
=(2√2+3√2)-24/(2√2-3√2)
=5√2+12√2
=17√2