a^2+b^2=6ab
a^2-2ab+b^2=4ab
(a-b)^2=4ab
a^2+2ab+b^2=8ab
(a+b)^2=8ab
[(a+b)/(a-b)]^2=8ab/4ab=2
a>b>0,a+b>0,a-b>0
(a+b)/(a-b)=根号2
(x+2)/(x+3)=m/(x+3)
x+2=m
x=m-2
增根就是分母为0
x+3=0
m-2+3=0
m=-1