若a≠0,a+6b=0则(1- a+2b分之b)÷a²-4b²分之（a+b）²的值

∵a+6b=0
∴a=-6b
∴[1- b/(a+2b)]÷[(a+b)²/(a²-4b²)]
=[1-b/(-6b+2b)]÷[(-6b+b)²/(36b²-4b²]
=[1+1/4]÷[25b²/(32b²)]
=5/4×32/25
=8/5
=1.4

a+6b=0
a=-6b
[1-b/（a+2b）]÷[(a+b)²/(a²-4b²)]
=[(a+2b-b)/(a+2b)]×[(a+2b)(a-2b)/(a+b)²]
=(a-2b)/(a+b)
=(-6b-2b)/(-6b+b)
=-8b/(-5b)
=8/5