∵a/2=b/3∴可设a=2k，b=3k，k≠0(5a-2b)/(a²-2b²)(a-2b)=(5a-2b)(a-2b)/(a²-2b²)=(5a²-12ab+4b²)/(a²-2b²)=(20k²-72k²+36k²)/(4k²-18k²)=(-16k²)/(-14k²)=8/7
