若a+2b=0,求分式a^2+2ab-b^2/2a^2+ab-b^2的值

问题描述:

若a+2b=0,求分式a^2+2ab-b^2/2a^2+ab-b^2的值

a+2b=0
a=-2b
(a²+2ab-b²)/(2a²+ab-b²)
=(4b²-4b²-b²)/(8b²-2b²-b²)
=-b²/(5b²)
=-1/5