第52页 - 启东中学作业本七年级数学苏科版宿迁专版

A

C

a-2

-b-a

-3y+4x

a²-4b²

$解：原式=a²-49.$

$ \begin{aligned}解：原式&=(2t)²-(3s)² \\ &=4t²-9s². \\ \end{aligned}$

$ \begin{aligned}解：原式&=(5n)²-m² \\ &=25n²-m². \\ \end{aligned}$

$ \begin{aligned}解：原式&=(\frac{1}{2}m)²-1² \\ &=\frac{1}{4}m²-1. \\ \end{aligned}$

$ \begin{aligned} 解：原式&=(-n^2)^2-(\frac{1}{4}m)^2 \\ &=n^{4}-\frac{1}{16}m^2. \\ \end{aligned}$

$ \begin{aligned}解：原式&=x²+2x+1-x²+1 \\ &=2x+2. \\ \end{aligned}$

A

D