【单选题】等比数列{an}满足a2+a4=20.则a3+a5=40. (1)公比q=2. (2)a1+a3=10.
C.
条件(1)和(2)单独都不充分,但条件(1)和条件(2)联合起来充分.
E.
条件(1)和(2)单独都不充分,条件(1)和条件(2)联合起来也不充分.
【简答题】The concentration of copper in a satnple of sea water is determined by anodic stripping voltammetry using the method of standard additions. When a 50.0-ml sample is yzed, the peak current is 0.886...
【简答题】写出下列分式有意义,值为0的条件. (1) x x 2 +1 (2) x-5 x (3) 2x-10 x-5 .
【简答题】There is 1000 grams of alcohol solution with the concentration of 15% inthe bottle,and now wepour 200 grams of alcohol solution A and 400 grams of alcohol solution B respectively,the concentration tur...
【简答题】已知a={2,-3,1),b={1,-2,3},求与a,b都垂直,且满足条件的向量c: (1)c为单位向量; (2)c·d=10,其中d={2,1,-7).
【单选题】已知a=(2,-3,-1),b=(1,-2,3),c=(1,-2,-7),若向量X满足条件:x⊥a,x⊥b,x·c=-10,则x为( )
【单选题】The writer seems to recommend that the concentration of concern should be placed on
A.
a better method of funding medical care.
B.
the way of employing medical fund.
C.
the threat to America's fiscal budget.
D.
how the fund is raised effectively.
【多选题】疗效评价需要回答的关键问题有哪些?
D.
除了需要评估的治疗措施外,两组是否得到相同的干预?