原式=[5a-2b/(a 2b)(a-2b)](a-2b) =5a-2b/a 2b 因为a/2=b/3≠0,所以3a=2b,带入上式 得:5a-2b/a 2b=5a-3a/a 3a=2a/4a=1/2
a/2=b/3∴2b=3a ∴:(5a-2b)/(a²-4b²)·(a-2b)=(5a-2b)/(a+2b)(a-2b)×(a-2b)=(5a-2b)/(a+2b)=(5a-3a)/(a+3a)=2a/4a=1/2