设X1〈 X2 且 X1,X2都属于{0,正无穷}Y1-Y2=根号下X1-根号下X2 =根号下X1-根号下X2 /1=X1-X2/根号下X1+根号下X2 因为：X1〈 X2 且 X1,X2都属于{0,正无穷}所以：根号下X1+根号下X2 〉0X1-X2〈0所以：Y1-Y2〈0Y1〈Y2所...