有關2by的精選大全

若直線ax+2by-2=0(a,b∈(0,+∞))平分圓x2+y2-4x-2y-6=0,則+的最小值是(  )...
問題詳情:若直線ax+2by-2=0(a,b∈(0,+∞))平分圓x2+y2-4x-2y-6=0,則+的最小值是()(A)4           (B)2(C)3-2         (D)3+2【回答】D.因為直線ax+2by-2=0平分圓x2+y2-4x-2y-6=0,所以圓心(2,1)在直線上,即2a+2b-2=0.∴a+b=1,∵a,b...
已知圓x2+y2-4ax+2by+b2=0(a>0,b>0)關於直線x-y-1=0對稱,那麼ab的...
問題詳情:已知圓x2+y2-4ax+2by+b2=0(a>0,b>0)關於直線x-y-1=0對稱,那麼ab的最大值是.【回答】 【解析】由圓x2+y2-4ax+2by+b2=0(a>0,b>0)關於直線x-y-1=0對稱,可得圓心(2a,-b)在直線x-y-1=0上,故有2a+b-1=0,即2a+b=1≥2,求得ab...
熱門標籤