2.若函数$f(x)=\left\{{\begin{array}{l}{{x^2}+(3-a)x+1,x≥0}\\{(a-1)x+2a-4,x<0}\end{array}}\right.$在R上为增函数,则a的取值范围为( )
A. | 1<a | B. | 1<a≤3 | C. | 1<a≤$\frac{5}{2}$ | D. | a≥3 |
20.已知函数y=f(1-x2)的定义域[-2,3],则函数g(x)=$\frac{f(2x+1)}{x+2}$的定义域是( )
A. | (-∞,-2)∪(-2,3] | B. | [-8,-2)∪(-2,1] | C. | [-$\frac{9}{2}$,-2)∪(-2,0] | D. | [-$\frac{9}{2}$,-2] |
19.已知函数f(x)=$\frac{2x+1}{x-1}$,其定义域是[-8,-4),则下列说法正确的是( )
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A. | f(x)有最大值$\frac{5}{3}$,无最小值 | B. | f(x)有最大值$\frac{5}{3}$,最小值$\frac{7}{5}$ | ||
C. | f(x)有最大值$\frac{7}{5}$,无最小值 | D. | f(x)有最大值2,最小值$\frac{7}{5}$ |