(上面打不出来的符号是向量的箭头)AB,3BC,4CA,51(已知点,,满足,,,则ABCAB,BC,BC,CA,CA,AB的值是_?(02(在中,,,,是边的中点,,,BAC120AB,2D,ABCAC,1BC则?((上面打不出来的符号是向量的箭头“?”)ADBC,,2aba3(若是与的等比中项,则的最大值为?(12,b12,bab,2*na,,a,4n4((本题满分16分)在数列中,a,3,(?2,且),数n,Na,,nn,11nnS列的前项和(a,,nn(1)证明:数列是等比数列,并求的通项公式;an,,21a,,,,nnS(2)求;nnS9,,nb(3)设,求的最大值(b,,2n,,nn10,,