x2y2xy315的知识精选

已知x,y∈R,x2+y2+xy=315,则x2+y2﹣xy的最小值是(  )A.35  B.105 C.14...
问题详情:已知x,y∈R,x2+y2+xy=315,则x2+y2﹣xy的最小值是()A.35  B.105 C.140D.210【回答】B【考点】7F:基本不等式.【分析】x,y∈R,x2+y2+xy=315,可得x2+y2=315﹣xy≥2xy,因此xy≤105.即可得出.【解答】解:∵x,y∈R,x2+y2+xy=315,∴x2+y2=3...
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