第156页 - 江苏版启东中学作业本七年级数学（上下册）

7

$\frac{25}{4}$

-4

-6或-10

-3或4

$ \begin{aligned}解:原式&=8x^6-x^6 \\ &=7x^6. \\ \end{aligned}$

$ \begin{aligned}解:原式&=b^{6n}·b^{12n}÷b^{5n+5} \\ &=b^{6n+12n-5n-5} \\ &=b^{13n-5}. \\ \end{aligned}$

$ \begin{aligned}解:原式&=-64a^{3m+3}÷8a^{2m+1} \\ &=-8a^{m+2}. \\ \end{aligned}$

$ \begin{aligned}解:原式&=(x-y)^9÷(x-y)^8-(x+y)^5÷(x+y)^4 \\ &=x-y-(x+y) \\ &=-2y. \\ \end{aligned}$

$ \begin{aligned} 解:原式&=9÷1-8-1 \\ &=0. \\ \end{aligned}$

$ \begin{aligned}解:原式&=-1-8-\frac{1}{16}×(-64) \\ &=-9+4 \\ &=-5. \\ \end{aligned}$