题目内容
20.计算:(1)2log210+log20.04;
(2)$\frac{lg3+2lg2-1}{lg1.2}$;
(3)$\sqrt{l{g}^{2}3-lg9+1}$;
(4)$\frac{1}{3}$log${\;}_{\frac{1}{6}}$8+2log${\;}_{\frac{1}{6}}$$\sqrt{3}$;
(5)log6$\frac{1}{12}$-2log63+$\frac{1}{3}$log627.
分析 根据对数的运算法则进行化简即可.
解答 解:(1)2log210+log20.04=log2100+log20.04=log2(100×0.04)=log24=2;
(2)$\frac{lg3+2lg2-1}{lg1.2}$=$\frac{lg3+lg4-lg10}{lg1.2}$=$\frac{lg\frac{3×4}{10}}{lg1.2}=\frac{lg1.2}{lg1.2}=1$;
(3)$\sqrt{l{g}^{2}3-lg9+1}$=$\sqrt{l{g}^{2}3-2lg3+1}=\sqrt{(lg3-1)^{2}}$=|lg3-1|=1-lg3;
(4)$\frac{1}{3}$log${\;}_{\frac{1}{6}}$8+2log${\;}_{\frac{1}{6}}$$\sqrt{3}$=log${\;}_{\frac{1}{6}}$8${\;}^{\frac{1}{3}}$+log${\;}_{\frac{1}{6}}$($\sqrt{3}$)2=log${\;}_{\frac{1}{6}}$2+log${\;}_{\frac{1}{6}}$3=log${\;}_{\frac{1}{6}}$6=-1;
(5)log6$\frac{1}{12}$-2log63+$\frac{1}{3}$log627=log6$\frac{1}{12}$-log632+log627${\;}^{\frac{1}{3}}$=log6$\frac{1}{12}$-log69+log63=log6($\frac{1}{12}×\frac{3}{9}$)=log6$\frac{1}{36}$=-2
点评 本题主要考查对数的化简,利用对数的运算法则是解决本题的关键.
A. | 奇函数 | B. | 偶函数 | ||
C. | 既是奇函数又是偶函数 | D. | 非奇非偶函数 |