4c9的知识精选

若a:b:c=3:5:7,且3a+2b-4c=9,则a+b+c的值等于( )A.-3             ...
问题详情:若a:b:c=3:5:7,且3a+2b-4c=9,则a+b+c的值等于( )A.-3              B.-5              C.-7               D.-15【回答】D【解析】已知a:b:c=3:5:7,设a=3k,b=5k,c=7...
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