9. (1)计算判断:$(\dfrac{2}{3})^{2}$_________$(\dfrac{3}{2})^{-2}$,$(\dfrac{5}{4})^{3}$_________$(\dfrac{4}{5})^{-3}$(填“$>$”“$<$”或“$=$”);
(2)猜想发现:$(\dfrac{a}{b})^{m}$_________$(\dfrac{b}{a})^{-m}$($a \neq 0$,$b \neq 0$,$m$是正整数,填“$>$”“$<$”或“$=$”);
(3)拓展应用:计算$(\dfrac{7}{15})^{-2} × (\dfrac{7}{5})^{2}$的结果为.
(2)猜想发现:$(\dfrac{a}{b})^{m}$_________$(\dfrac{b}{a})^{-m}$($a \neq 0$,$b \neq 0$,$m$是正整数,填“$>$”“$<$”或“$=$”);
(3)拓展应用:计算$(\dfrac{7}{15})^{-2} × (\dfrac{7}{5})^{2}$的结果为.
答案:9.(1)= = (2)=
(3)9 解析$:(\frac{7}{15})^{-2}×(\frac{7}{5})^2=(\frac{15}{7})^2×(\frac{7}{5})^2=9.$
(3)9 解析$:(\frac{7}{15})^{-2}×(\frac{7}{5})^2=(\frac{15}{7})^2×(\frac{7}{5})^2=9.$
10. 计算:
(1)$4^{-9} × (-4^{18}) ÷ 4^{7} =$
(2)$(3x^{4}y^{-5})^{-2} =$
(1)$4^{-9} × (-4^{18}) ÷ 4^{7} =$
-16
;(2)$(3x^{4}y^{-5})^{-2} =$
$\frac{y^{10}}{9x^8}$
.答案:$10.(1)-16 (2)\frac{y^{10}}{9x^8}$
解析:
(1) $4^{-9} × (-4^{18}) ÷ 4^{7} = -4^{-9 + 18 - 7} = -4^{2} = -16$;
(2) $(3x^{4}y^{-5})^{-2} = 3^{-2}x^{-8}y^{10} = \frac{y^{10}}{9x^{8}}$
(2) $(3x^{4}y^{-5})^{-2} = 3^{-2}x^{-8}y^{10} = \frac{y^{10}}{9x^{8}}$
11. 若$m$,$n$满足$3m - n - 4 = 0$,则$8^{m} ÷ 2^{n}$的值为
16
.答案:11.16
解析:
由$3m - n - 4 = 0$,得$3m - n = 4$。
$8^{m} ÷ 2^{n} = (2^{3})^{m} ÷ 2^{n} = 2^{3m} ÷ 2^{n} = 2^{3m - n}$。
因为$3m - n = 4$,所以$2^{3m - n} = 2^{4} = 16$。
16
$8^{m} ÷ 2^{n} = (2^{3})^{m} ÷ 2^{n} = 2^{3m} ÷ 2^{n} = 2^{3m - n}$。
因为$3m - n = 4$,所以$2^{3m - n} = 2^{4} = 16$。
16
12. 计算:
(1)$-(2 - \pi)^{0} + (-2^{4}) + (\dfrac{2}{3})^{-3}$;
(2)$x^{3} ÷ x^{-5} - (2x^{4})^{2} + x^{10} ÷ (-x)^{2}$;
(3)$(-3a^{3})^{2} - 2a^{6} - (2a)^{-3} ÷ (2a)^{-9}$;
(4)$|-2| + (\pi - 3)^{0} + (-\dfrac{1}{3})^{-2} + (-1)^{222}$.
(1)$-(2 - \pi)^{0} + (-2^{4}) + (\dfrac{2}{3})^{-3}$;
(2)$x^{3} ÷ x^{-5} - (2x^{4})^{2} + x^{10} ÷ (-x)^{2}$;
(3)$(-3a^{3})^{2} - 2a^{6} - (2a)^{-3} ÷ (2a)^{-9}$;
(4)$|-2| + (\pi - 3)^{0} + (-\dfrac{1}{3})^{-2} + (-1)^{222}$.
答案:$12.(1)-13\frac{5}{8} (2)-2x^8 (3)-57a^6 (4)13$
解析:
(1)$-(2 - \pi)^{0} + (-2^{4}) + (\dfrac{2}{3})^{-3}$
$=-1 + (-16) + \dfrac{27}{8}$
$=-17 + 3\dfrac{3}{8}$
$=-13\dfrac{5}{8}$
(2)$x^{3} ÷ x^{-5} - (2x^{4})^{2} + x^{10} ÷ (-x)^{2}$
$=x^{3 - (-5)} - 4x^{8} + x^{10} ÷ x^{2}$
$=x^{8} - 4x^{8} + x^{8}$
$=-2x^{8}$
(3)$(-3a^{3})^{2} - 2a^{6} - (2a)^{-3} ÷ (2a)^{-9}$
$=9a^{6} - 2a^{6} - (2a)^{-3 - (-9)}$
$=7a^{6} - (2a)^{6}$
$=7a^{6} - 64a^{6}$
$=-57a^{6}$
(4)$|-2| + (\pi - 3)^{0} + (-\dfrac{1}{3})^{-2} + (-1)^{222}$
$=2 + 1 + 9 + 1$
$=13$
$=-1 + (-16) + \dfrac{27}{8}$
$=-17 + 3\dfrac{3}{8}$
$=-13\dfrac{5}{8}$
(2)$x^{3} ÷ x^{-5} - (2x^{4})^{2} + x^{10} ÷ (-x)^{2}$
$=x^{3 - (-5)} - 4x^{8} + x^{10} ÷ x^{2}$
$=x^{8} - 4x^{8} + x^{8}$
$=-2x^{8}$
(3)$(-3a^{3})^{2} - 2a^{6} - (2a)^{-3} ÷ (2a)^{-9}$
$=9a^{6} - 2a^{6} - (2a)^{-3 - (-9)}$
$=7a^{6} - (2a)^{6}$
$=7a^{6} - 64a^{6}$
$=-57a^{6}$
(4)$|-2| + (\pi - 3)^{0} + (-\dfrac{1}{3})^{-2} + (-1)^{222}$
$=2 + 1 + 9 + 1$
$=13$
13. (易错题)若$(x - 2)^{x + 1} = 1$,求$x$的值.
答案:13.①当x+1=0且x-2≠0时,满足题意,此时x=-1;
②当x-2=1时,满足题意,此时x=3;③当x-2=-1且x+1为偶数时,满足题意,此时x=1.综上所述,x的值为-1或3或1 [易错分析]考虑不全面,只注意到$a^0=1(a≠0)$和1的任意次幂都等于0,而漏考虑-1的偶数次幂也等于1.
②当x-2=1时,满足题意,此时x=3;③当x-2=-1且x+1为偶数时,满足题意,此时x=1.综上所述,x的值为-1或3或1 [易错分析]考虑不全面,只注意到$a^0=1(a≠0)$和1的任意次幂都等于0,而漏考虑-1的偶数次幂也等于1.