题目内容
9.计算下列各式:(1)($\frac{36}{49}$)${\;}^{\frac{3}{2}}$;
(2)2$\sqrt{3}$×$\root{3}{1.5}$×$\root{6}{12}$;
(3)a${\;}^{\frac{1}{2}}$a${\;}^{\frac{1}{4}}$a${\;}^{-\frac{1}{8}}$;
(4)2x${\;}^{-\frac{1}{3}}$($\frac{1}{2}$x${\;}^{\frac{1}{3}}$-2x${\;}^{-\frac{2}{3}}$).
分析 (1)($\frac{36}{49}$)${\;}^{\frac{3}{2}}$=$(\frac{6}{7})^{2×\frac{3}{2}}$,从而化简可得;
(2)2$\sqrt{3}$×$\root{3}{1.5}$×$\root{6}{12}$=$\root{6}{1{2}^{3}×\frac{{3}^{2}}{{2}^{2}}×12}$,从而化简可得;
(3)a${\;}^{\frac{1}{2}}$a${\;}^{\frac{1}{4}}$a${\;}^{-\frac{1}{8}}$=${a}^{\frac{1}{2}+\frac{1}{4}-\frac{1}{8}}$,从而化简可得;
(4)2x${\;}^{-\frac{1}{3}}$($\frac{1}{2}$x${\;}^{\frac{1}{3}}$-2x${\;}^{-\frac{2}{3}}$)=2$•\frac{1}{2}$${x}^{-\frac{1}{3}+\frac{1}{3}}$-2•2•${x}^{-\frac{1}{3}-\frac{2}{3}}$,从而化简可得.
解答 解:(1)($\frac{36}{49}$)${\;}^{\frac{3}{2}}$=$(\frac{6}{7})^{2×\frac{3}{2}}$=$\frac{{6}^{3}}{{7}^{3}}$=$\frac{216}{343}$,
(2)2$\sqrt{3}$×$\root{3}{1.5}$×$\root{6}{12}$=$\root{6}{1{2}^{3}×\frac{{3}^{2}}{{2}^{2}}×12}$=2×3=6;
(3)a${\;}^{\frac{1}{2}}$a${\;}^{\frac{1}{4}}$a${\;}^{-\frac{1}{8}}$=${a}^{\frac{1}{2}+\frac{1}{4}-\frac{1}{8}}$=${a}^{\frac{5}{8}}$,
(4)2x${\;}^{-\frac{1}{3}}$($\frac{1}{2}$x${\;}^{\frac{1}{3}}$-2x${\;}^{-\frac{2}{3}}$)
=2$•\frac{1}{2}$${x}^{-\frac{1}{3}+\frac{1}{3}}$-2•2•${x}^{-\frac{1}{3}-\frac{2}{3}}$
=1-4x-1.
点评 本题考查了有理指数幂的运算.
A. | -6 | B. | -8 | C. | -12 | D. | -14 |
A. | 3 | B. | 5 | C. | 4 | D. | 6 |