第10页 - 伴你学活页卷七年级数学苏科版

$12x^{4}-2x^{3}+6x^{2}$

$-16m^{4}n^{3}$

$22a^{2}$

4

8

$±3$

$a^{2}-ab + b^{2}$

625

$ 解： (-a^2b^3-\frac {1}{3}ab+2bc)(-\frac {3}{4}a^2b) $

$=\frac {3}{4}a^4b^4+\frac {1}{4}a^3b^2-\frac {3}{2}a^2b^2c$

 解：$\begin{aligned}&(x + y)(x^{2}+y^{2})(x - y)(x^{4}+y^{4})\\=&[(x + y)(x - y)](x^{2}+y^{2})(x^{4}+y^{4})\\=&(x^{2}-y^{2})(x^{2}+y^{2})(x^{4}+y^{4})\\=&(x^{4}-y^{4})(x^{4}+y^{4})\\=&x^{8}-y^{8}\end{aligned}$

 解：$\begin{aligned}&(a - 2b + 3)(a + 2b - 3)\\=&[a-(2b - 3)][a+(2b - 3)]\\=&a^{2}-(2b - 3)^{2}\\=&a^{2}-(4b^{2}-12b + 9)\\=&a^{2}-4b^{2}+12b - 9\end{aligned}$

$解:原式=3x^{2}-12-(3x^{2}+x-4)$

$=-x-8$

$解:原式=x^{2}+4x+4+4x^{2}-1-4x^{2}-4x=x^{2}+3$

$把x=-2代入原式=4+3=7$