因为a方+b方—6ab=0
两边除以b方
(a/b)方-6(a/b)+1=0
将a/b看成未知数,
解得a/b=3+2√2或3-2√2(舍去,因为a>b,所以a/b>1)
（a+b）/(b-a)=[(a/b)+1]/[1-(a/b)]
=(4+2√2)/(-2-2√2)
=-(2+√2)/(1+√2)
=-(2+√2)(√2-1)
=-2√2+2-2+√2
=-√2