原式=2/3a-[2/(a+b)]{[(a+b)/3a]-(a+b)}÷[(a-b)/b]
乘进去
=2/3a-[2/3a-2]×[b/(a-b)]
=2/3a-(2-6a)/3a×[b/(a-b)]
=2/3a-(2b-6ab)/3a(a-b)
=(2a-2b-2b+6ab)/(3a^2-3ab)
=(2a-4b+6ab)/(3a^2-3ab)
原式=2/3a-[2/(a+b)]{[(a+b)/3a]-(a+b)}÷[(a-b)/b]
乘进去
=2/3a-[2/3a-2]×[b/(a-b)]
=2/3a-(2-6a)/3a×[b/(a-b)]
=2/3a-(2b-6ab)/3a(a-b)
=(2a-2b-2b+6ab)/(3a^2-3ab)
=(2a-4b+6ab)/(3a^2-3ab)