第14页 - 伴你学活页卷七年级数学苏科版

B

$x^{2}+x - 6$

$4mn$

$(12a+36)$

$2x^{2}y^{3}$

11

$2x^{2}+7x - 4$

±24

C

$(2m+n)^2=4\ \mathrm {m^2}+4mn+n^2$

 解：$\begin{aligned}(-5ab^{2}x)\cdot(-\frac{3}{10}a^{2}bx^{3}y)&=(-5)\times(-\frac{3}{10})a^{1 + 2}b^{2+1}x^{1 + 3}y\\&=\frac{3}{2}a^{3}b^{3}x^{4}y\end{aligned}$

 解：$\begin{aligned}(\frac{1}{2}x^{2}y - 2xy + y^{2})\cdot(-4xy)&=\frac{1}{2}x^{2}y\cdot(-4xy)-2xy\cdot(-4xy)+y^{2}\cdot(-4xy)\\&=-2x^{3}y^{2}+8x^{2}y^{2}-4xy^{3}\end{aligned}$