1.已知等差数列{an},{bn}的前n项和分别为Sn,Tn,且$\frac{S_n}{T_n}=\frac{9n+59}{n+3}$,则使得$\frac{a_n}{b_n}$为整数的正整数的个数是( )
A. | 5 | B. | 4 | C. | 3 | D. | 2 |
18.观察下列的规律:$\frac{1}{1},\frac{1}{2},\frac{2}{1}$,$\frac{1}{3},\frac{2}{2},\frac{3}{1}$,$\frac{1}{4},\frac{2}{3},\frac{3}{2},\frac{4}{1}$…则第93个是( )
A. | $\frac{1}{8}$ | B. | $\frac{2}{13}$ | C. | $\frac{8}{7}$ | D. | $\frac{1}{14}$ |
17.已知函数$f(x)=\frac{1}{1-x}+lnx$,且f(x0)=0,若a∈(1,x0),b∈(x0,+∞),则( )
A. | f(a)<0,f(b)<0 | B. | f(a)>0,f(b)>0 | C. | f(a)>0,f(b)<0 | D. | f(a)<0,f(b)>0 |
15.已知不等式|x+a|+|x-3|≤|x-4|的解集包含[2,3],则a的取值范围为( )
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A. | [-3,-2] | B. | [-2,0] | C. | [-3,0] | D. | [-2,1] |