若a+3b=0,则(1-b/a+2b)÷a^2+2ab+b^2/a^2-4b^2

若a+3b=0,则(1-b/a+2b)÷a^2+2ab+b^2/a^2-4b^2
若a+3b=0,则(1-b/a+2b)÷a^2+2ab+b^2/a^2-4b^2

若a+3b=0,则(1-b/a+2b)÷a^2+2ab+b^2/a^2-4b^2
a+3b=0
a=-3b
原式=[(a+2b-b)/(a+2b)]÷(a+b)^2/(a+2b)(a-2b)
=(a+b)/(a+2b)×(a+2b)(a-2b)/(a+b)^2
=(a-2b)/(a+b)
=(-3b-2b)/(-3b+b)
=-5b/(-2b)
=5/2

a+3b=0，a=-3b
{ 1 - b/(a+2b)} ÷ { (a^2+2ab+b^2)/(a^2-4b^2) }
= { (a+2b-b)/(a+2b)} × { (a^2-4b^2) / (a^2+2ab+b^2) }
= (a+b)/(a+2b) × (a+2b)(a-2b) / (a+b)^2
= (a-2b) / (a+b)
= (-3b-2b) / (-3b+b)
= (-5)/(-2)
=2.5