第46页 - 启东中学作业本七年级数学苏科版宿迁专版

D

B

22x²-24x

5a⁵-10a⁴+5a³

3x²

$解：原式=-8x²+6x.$

$ \begin{aligned}解：原式&=\frac{3}{4}ab^2·\frac{1}{3}ab-3ab·\frac{1}{3}ab \\ &=\frac{1}{4}a^2b^3-a^2b^2. \\ \end{aligned}$

$ \begin{aligned}解：原式&=4x^2·(x-3) \\ &=4x^3-12x^2. \\ \end{aligned}$

（更多请查看作业精灵详解）

$ \begin{aligned} 解：原式&=-xy^2+3x^2y+3xy^2 \\ &=3x^2y+2xy^2. \\ \end{aligned}$

$ \begin{aligned}解：原式&=3a^2+3a-2a^2+2a \\ &=a^2+5a. \\ \end{aligned}$

B

A

$解:这块地的面积为3x(2x-y)+(3x+2y)(3x+x)+ x(2x-y)$

$ \begin{aligned}&=6x^2-3xy+12x^2+8xy+2x^2-xy \\ &=20x^2+ 4xy. \\ \end{aligned}$