搜索
1.计算.
(1)$-5xy^{2}·(2x)^{3}$.
(2)$(a+b)(a-b)-a(a-2b)$.
(3)$(8x^{4}-6x^{3})÷(-2x^{2})$.
(4)$(2x-1)^{2}-(2x+3)(2x-3)$.
(5)$(2a^{2}-1)(a-4)$.
(6)$(2x+3y)^{2}-(2x+y)(2x-y)$.
(1)$-5xy^{2}·(2x)^{3}$.
(2)$(a+b)(a-b)-a(a-2b)$.
(3)$(8x^{4}-6x^{3})÷(-2x^{2})$.
(4)$(2x-1)^{2}-(2x+3)(2x-3)$.
(5)$(2a^{2}-1)(a-4)$.
(6)$(2x+3y)^{2}-(2x+y)(2x-y)$.
答案：
1.
(1)$-40x^{4}y^{2}$.
(2)$2ab - b^{2}$.
(3)$-4x^{2}+3x$.
(4)$-4x + 10$.
(5)$2a^{3}-8a^{2}-a + 4$.
(6)$12xy + 10y^{2}$.
(1)$-40x^{4}y^{2}$.
(2)$2ab - b^{2}$.
(3)$-4x^{2}+3x$.
(4)$-4x + 10$.
(5)$2a^{3}-8a^{2}-a + 4$.
(6)$12xy + 10y^{2}$.
2.(1)已知$a+3b=4$，求$3^{a}×27^{b}$的值.
(2)若$2^{x}=3$，求$2^{3x+2}·2^{2x}$的值.
(2)若$2^{x}=3$，求$2^{3x+2}·2^{2x}$的值.
答案：
2.解：
(1)$\because a + 3b = 4$,
$\therefore$原式$=3^{a}×(3^{3})^{b}=3^{a}×3^{3b}=3^{a + 3b}=3^{4}=81$.
(2)$\because2^{x}=3$,$\therefore$原式$=2^{3x + 2 + 2x}=2^{5x + 2}=2^{5x}×2^{2}=$
$(2^{x})^{5}×2^{2}=3^{5}×2^{2}=972$.
(1)$\because a + 3b = 4$,
$\therefore$原式$=3^{a}×(3^{3})^{b}=3^{a}×3^{3b}=3^{a + 3b}=3^{4}=81$.
(2)$\because2^{x}=3$,$\therefore$原式$=2^{3x + 2 + 2x}=2^{5x + 2}=2^{5x}×2^{2}=$
$(2^{x})^{5}×2^{2}=3^{5}×2^{2}=972$.
3.先化简，再求值.
(1)$\frac{x^{2}+4x+4}{x^{2}+2x}÷(2x-\frac{4+x^{2}}{x})$，其中$x=5$.
(2)$(\frac{m}{m-1}-1)÷\frac{m^{3}-m}{m^{2}-2m+1}$，其中$m=2$.
(1)$\frac{x^{2}+4x+4}{x^{2}+2x}÷(2x-\frac{4+x^{2}}{x})$，其中$x=5$.
(2)$(\frac{m}{m-1}-1)÷\frac{m^{3}-m}{m^{2}-2m+1}$，其中$m=2$.
答案：
3.
(1)解：原式$=\frac{1}{x - 2}$.当$x = 5$时，原式$=\frac{1}{3}$.
(2)解：原式$=\frac{1}{m^{2}+m}$.当$m = 2$时，原式$=\frac{1}{6}$.
(1)解：原式$=\frac{1}{x - 2}$.当$x = 5$时，原式$=\frac{1}{3}$.
(2)解：原式$=\frac{1}{m^{2}+m}$.当$m = 2$时，原式$=\frac{1}{6}$.
查看更多完整答案，请扫码查看
