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第76页

信息发布者：

$-x^{9}$

$3x^{2}$

$x^{4}y^{2}$

$6n + 5$

$(2a + 8b + 4ab)$

 解：$\begin{aligned}(-a^{2})^{3}\div(-a)^{2}&=-a^{6}\div a^{2}\\&=-a^{6 - 2}\\&=-a^{4}\end{aligned}$

 解：$\begin{aligned}(-45a^{3}b^{7})\div(-9a^{3}b^{4})&=( - 45\div(-9))\times(a^{3}\div a^{3})\times(b^{7}\div b^{4})\\&=5\times1\times b^{7 - 4}\\&=5b^{3}\end{aligned}$

 解：$\begin{aligned}(8\times10^{9})\div(-4\times10^{7})&=[8\div(-4)]\times(10^{9}\div10^{7})\\&=-2\times10^{9 - 7}\\&=-2\times10^{2}\end{aligned}$

 解：$\begin{aligned}&(2x^{3}y^{2}-3x^{2}y^{3})\div(\frac{1}{2}xy)^{2}\\=&(2x^{3}y^{2}-3x^{2}y^{3})\div\frac{1}{4}x^{2}y^{2}\\=&2x^{3}y^{2}\div\frac{1}{4}x^{2}y^{2}-3x^{2}y^{3}\div\frac{1}{4}x^{2}y^{2}\\=&(2\div\frac{1}{4})\times(x^{3}\div x^{2})\times(y^{2}\div y^{2})-(3\div\frac{1}{4})\times(x^{2}\div x^{2})\times(y^{3}\div y^{2})\\=&8x - 12y\end{aligned}$