19.2${\;}^{1-\frac{1}{2}lo{g}_{2}3}$的值等于( )
A. | $\frac{2}{3}$ | B. | 2$\sqrt{3}$ | C. | $\frac{2}{3}$$\sqrt{3}$ | D. | 2 |
18.已知函数f(x)=$\left\{\begin{array}{l}{{x}^{2},x>0}\\{x+1,x≤0}\end{array}\right.$,若f(a)-f(1)=0,则实数a的值等于( )
A. | -1或0 | B. | -1或1 | C. | 1或0 | D. | 1 |
17.函数y=$\frac{1}{{x}^{2}}$(x∈R)的值域是( )
A. | (-∞,0) | B. | (0,+∞) | C. | (-∞,0)∪(0,+∞) | D. | R |
16.已知lg2=a,1g7=b,则log1498=( )
A. | $\frac{a-b}{a+b}$ | B. | $\frac{2a+b}{a+b}$ | C. | $\frac{a-2b}{a+b}$ | D. | $\frac{a+2b}{a+b}$ |
11.已知125x=1000,12.5y=1000,则$\frac{1}{x}$$-\frac{1}{y}$的值为( )
0 250952 250960 250966 250970 250976 250978 250982 250988 250990 250996 251002 251006 251008 251012 251018 251020 251026 251030 251032 251036 251038 251042 251044 251046 251047 251048 251050 251051 251052 251054 251056 251060 251062 251066 251068 251072 251078 251080 251086 251090 251092 251096 251102 251108 251110 251116 251120 251122 251128 251132 251138 251146 266669
A. | 1 | B. | 2 | C. | 0 | D. | $\frac{1}{3}$ |